JP5045262B2 - Electric melting furnace - Google Patents

Description

  The present invention relates to an electric melting furnace.

  In general, high-level radioactive liquid waste generated at nuclear facilities is melted in an electric melting furnace of the high-level radioactive liquid waste glass solidification facility, treated as a glass solid, and then stored in a radioactive waste storage facility. The

  In the vitrification facility, when melting the raw glass as a material to be melted inside the electric melting furnace, a high level radioactive waste liquid is mixed, and the molten glass mixed with the high level radioactive waste liquid is a canister (stainless steel container). The glass solidified body is formed by injecting into molten glass and solidifying the molten glass.

  FIG. 13 shows an example of a conventional electric melting furnace. The electric melting furnace includes a melting furnace body 3 constructed of a refractory material 2 such as a refractory brick so that a melting space 1 is formed therein. The upper ceiling wall of the melting furnace body 3 is provided with an inlet 4 into which high-level radioactive waste liquid as a liquid to be treated and raw glass such as glass beads as a material to be melted are charged. A main electrode 5 that heats and melts the raw glass in the melting space 1 by energization between each other is disposed opposite to the middle portion of the inner wall in the vertical direction, and is constricted in a conical shape in the melting furnace body 3. A bottom electrode 6 that heats and melts the glass in the bottom of the melting space 1 by energization with the main electrode 5 is disposed at the bottom of the bottom, and the bottom of the melting furnace body 3 in which the bottom electrode 6 is disposed. The flow-down port 7 is formed in the bottom.

  Connected to the main electrode 5 is a single-phase AC main electrode power source 9 which has terminals for S phase and R phase and has a main electrode transformer 8 for energizing between the main electrodes 5. A thyristor 10 serving as a main electrode switching element is provided on the R phase side of the primary coil side of the main electrode transformer 8 of the main power supply 9 and one of the main electrode 5 shared with the bottom electrode 6 has an S phase. And a single-phase AC bottom electrode power supply 12 having a bottom electrode transformer 11 for energizing between one of the main electrode 5 shared with the bottom electrode 6 and having an R-phase terminal. A thyristor 13 as a bottom electrode switching element is provided on the R phase side of the primary coil side of the bottom electrode transformer 11 of the electrode power source 12.

  In FIG. 13, 14 is a main electrode voltmeter for measuring the voltage passed between the main electrodes 5, 15 is a main electrode ammeter for measuring the current passed between the main electrodes 5, Reference numeral 16 denotes a bottom electrode voltmeter for measuring a voltage applied between the bottom electrode 6 and one of the main electrodes 5, and reference numeral 17 denotes a current supplied between the bottom electrode 6 and one of the main electrodes 5. It is an ammeter for bottom electrodes for measuring.

  In the electric melting furnace as described above, high-level radioactive waste liquid and raw glass are introduced from the inlet 4 of the melting furnace main body 3, and first, an electric current is passed between the main electrodes 5 to cause Joule heat of the molten glass therebetween. The high-level radioactive liquid near the surface layer and the raw glass are sufficiently melted together. Subsequently, a current is passed between the main electrode 5 and the bottom electrode 6 to heat the glass on the top of the bottom electrode 6 by Joule heat. The solidified glass clogged inside the mouth 7 is melted and extracted downward, whereby the molten glass in the melting furnace main body 3 is caused to flow down into a canister (not shown) set at the lower part thereof and hermetically accommodated as a glass solidified body. It is supposed to be.

  Incidentally, the voltage supplied between the main electrodes 5 is measured by the main electrode voltmeter 14, the current supplied between the main electrodes 5 is measured by the main electrode ammeter 15, and the voltage between the bottom electrode 6 and the main electrode 5 is measured. The voltage supplied between the electrodes is measured by the bottom electrode voltmeter 16, and the current supplied between the bottom electrode 6 and one of the main electrodes 5 is measured by the bottom electrode ammeter 17.

  By the way, in the electric circuit as described above, the thyristors 10 and 13 are exclusively used for controlling the amount of power supplied to the main electrode 5 and the bottom electrode 6 and are effective for this purpose. , To avoid current interference between the electrodes when a plurality of pairs of electrodes (main electrodes 5 and main electrode 5 and bottom electrode 6) are simultaneously energized from separate main electrode power source 9 and bottom electrode power source 12 It cannot be a means.

  Now, when the main electrode power supply 9 is energized between the main electrodes 5, most of the current flowing between the main electrodes 5 flows in the a direction through the molten glass, but a part flows in the b direction. The electric current in the b direction flows in the c direction as it is when the electric circuit connecting the bottom electrode 6, the main electrode 5, the bottom electrode transformer 11 and the bottom electrode power source 12 is not connected. Part of the current flows in the d direction. In this case, when the internal resistance of the electric circuit from the bottom electrode 6 and the main electrode 5 to the bottom electrode power source 12 through the bottom electrode transformer 11 is small, the amount of current flowing in the d direction increases. As a result of so-called current interference that current flows into the bottom electrode transformer 11 connected to the bottom electrode 6 and the main electrode 5, the power supply control of the bottom electrode power supply 12 is hindered. Similarly, when power is supplied between the bottom electrode 6 and the main electrode 5 from the bottom electrode power source 12, a part of the current flowing between the bottom electrode 6 and the main electrode 5 is connected to the main electrode 5. 8 and current interference occurs, resulting in a failure in power supply control of the main electrode power source 9.

  In such an electric melting furnace, in order to realize proper power feeding to the main electrode 5 and the bottom electrode 6, it is necessary to prevent the above-described current interference that hinders power feeding control. That is, the interference current flows to the secondary coil side of the main electrode transformer 8 and the bottom electrode transformer 11 through the mutual main electrode 5 and the bottom electrode 6, so that the thyristors 10 and 13 are connected to the primary coil side. In the conventional electric circuit, the thyristors 10 and 13 do not act to block the interference current, and as a result, the influence of the current interference cannot be avoided.

  An electric melting furnace as shown in FIG. 14 has been proposed in order to prevent the occurrence of current interference as described above and to enable stable power supply control in each of the main electrode power source 9 and the bottom electrode power source 12. The electric melting furnace is provided with a thyristor 10 as a main electrode switching element on the R phase side on the secondary coil side of the main electrode transformer 8 of the main electrode power source 9 and a thyristor 13 as a bottom electrode switching element. The bottom electrode transformer 11 of the bottom electrode power source 12 is provided on the R phase side on the secondary coil side. In FIG. 14, the same reference numerals as those in FIG. 13 denote the same components.

  In the electric melting furnace shown in FIG. 14, when the R phase of each of the main electrode power source 9 and the bottom electrode power source 12 is positive, a thyristor ignition circuit (not shown) is applied to the gate electrode of the element S1 of the thyristor 10. Consider a case where a thyristor firing signal for supplying power between the main electrodes 5 is sent. Further, it is assumed that a thyristor ignition signal for supplying power between one of the main electrodes 5 and the bottom electrode 6 is not sent from the thyristor ignition circuit to the gate electrode of the element T2 of the thyristor 13. At this time, since the elements T2 and S2 of the thyristor 13 are also in the arc extinguishing state, an electric circuit leading from the bottom electrode 6 to one of the main electrodes 5 via the thyristor 13 and the bottom electrode transformer 11 is not formed. As a result, current from the main electrode power source 9 does not flow into the bottom electrode transformer 11 connected to the bottom electrode 6 via the bottom electrode 6, and is necessary for heating and melting the glass between the main electrodes 5. Only electric power is supplied from the main electrode power source 9. Similarly, in the reverse case, the current from the main electrode power source 9 does not flow into the bottom electrode transformer 11 connected to the bottom electrode 6 and one of the main electrodes 5 via the bottom electrode 6. Only the electric power necessary for heating and melting the glass is supplied from the bottom electrode power source 12 between the electrode 6 and one of the main electrodes 5.

For example, Patent Document 1 shows a general technical level related to the electric melting furnace as described above.
Japanese Patent Laid-Open No. 11-38186

However, the inventor has found that there is a problem that is not Oite also resolved to an electric melting furnace as shown in FIG. 14. This is a defect in the effective voltage value calculation due to voltage interference, which will be described in detail below.

The conduction start points (ignition angles) of the thyristors 10 and 13 are α and β, the energization voltages are v ₁ and v ₂ , and the peak values of the main electrode power source 9 and the bottom electrode power source 12 as sine wave AC power sources are 2 ^{1. Assuming that / 2} V ₁ and 2 ^1/2 V ₂ , thyristor energization is expressed by the following equation.

参照）。これを電圧干渉と呼ぶことにする。ここで

は測定電圧とする。又、Ｒ₁ 、Ｒ₂ 、Ｒ₃は各電極５，６間で測定される（集中定数化された）抵抗値とする。 Normally, the cycle is a phase angle of 360 °, but here the cycle T is set to a phase angle of 180 ° for the sake of simplification of the expression [Formula 1]. Further, the generality of the negative sign sine wave in parentheses is not lost even if the description is omitted.
Since the main electrode power source 9 and the bottom electrode power source 12 are controlled separately (in accordance with their respective purposes), generally α ≠ β, and only one of them is energized. FIG. 15 shows an example of a state in which β is fired first. In a section where the time or phase is β or more and less than α, the non-energized voltmeter (for example, the main electrode voltmeter 14) is connected to the energized voltmeter (for example, the bottom electrode voltmeter 16). ) Is divided by the resistance in the furnace (measured in FIG. 16).

reference). This is called voltage interference. here

Is the measured voltage. R ₁ , R ₂ , and R ₃ are resistance values measured between the electrodes 5 and 6 (concentrated constants).

とすると、測定電圧は次のように表現される。

And

Then, the measured voltage is expressed as follows.

Accordingly, the measured voltage effective value is expressed as follows.

  Here, the first term in the square root on the right side means the divided apparent voltage effective value shown in FIG. Incidentally, if T in Equation [6] is T ′ and T ′ = 2T, the value is the same as the 360 ° period calculation.

On the other hand, the net effective voltage value energized by the main electrode power source 9 and the bottom electrode power source 12 should be given by the following equation.

  When [Expression 6] actually measured and calculated is compared with the ideal [Expression 7], the first term in the square root of the right side of [Expression 6] is expressed by [Expression 7] due to voltage interference. It can be seen that they do not match and do not represent the net effective voltage value. Therefore, when measuring the effective voltage value, it is necessary to calculate the effective value by excluding the first term in the square root of the right side of [Formula 6].

However, as shown in FIG. 17, a conventional main electrode voltage effective value calculation circuit 18 ′ includes a multiplier 19 that squares an instantaneous voltage value v ₁ and an integrator that integrates the operation result of the multiplier 19. 20, a root calculator 21 for obtaining the square root of the calculation result in the integrator 20, and a hold circuit 22 for holding the calculation result in the root calculator 21. Similarly, the conventional bottom electrode voltage effective value calculation circuit 23 ′ calculates the square of the instantaneous voltage value v ₂ , and the calculation result of the multiplier 24. Are integrated, a root calculator 26 for obtaining the square root of the calculation result in the integrator 25, and a hold circuit 27 for holding the calculation result in the root calculator 26. The net voltage It was not possible to determine the value. Since the integration in the integrators 20 and 25 is reset every period, hold circuits 22 and 27 are provided.

  Incidentally, the above problem also exists in the electric melting furnace shown in FIG.

  13 has the merit that the current capacity of the thyristors 10 and 13 can be reduced and the cost can be reduced, whereas the circuit system shown in FIG. 14 has the transformer 8 for the main electrode and the bottom electrode. Since the secondary coil side of the transformer 11 has a low voltage and a large current, the current capacity of the thyristors 10 and 13 must be designed to be large, which makes it difficult to reduce costs.

  In the following, the circuit method of FIG. 13 will be considered with respect to the calculation of the effective current value.

は測定電流・電圧とする。 Since the main electrode power source 9 and the bottom electrode power source 12 are controlled separately (in accordance with their respective purposes), generally α ≠ β, and only one of them is energized. At this time, the electrical circuit on the non-energized side is always in a conductive state between the secondary coil side of the transformer (8 or 11) and the electrode (5 or 6). For this reason, the voltage on the energization side (in the example of FIG. 18) is divided by the resistance in the furnace and applied to the secondary coil side terminal of the non-energization side transformer (8 or 11). Since the thyristor (10 or 13) connected to the primary coil side of the non-energized transformer (8 or 11) is in the arc extinguishing state, it is in an open (no load) state when viewed from the voltage on the secondary coil side. . As a result, an exciting current flows through the secondary coil side circuit of the transformer (8 or 11) and is added to the non-energized ammeter effective value calculation. This is called current interference. here

Is measured current and voltage.

At this time, the measured current is expressed by the following equation. Here, i ₁ and i ₂ are currents when both thyristors 10 and 13 are ignited, and i _1m and i _2m are excitation currents based on voltages divided by the resistance in the furnace.

Therefore, the measured current effective value is expressed as follows.

  Here, the first term in the square root on the right side means the exciting current by the divided voltage shown in FIG. Incidentally, if T in Equation [10] is T ′ and T ′ = 2T, the value is the same as the 360 ° period calculation.

On the other hand, the net effective current value energized by the main electrode power source 9 and the bottom electrode power source 12 should be given by the following equation.

  Comparing [Equation 10], which is actually measured and calculated, with the ideal [Equation 11], the first term in the square root of the right side of [Equation 10] agrees with [Equation 11] due to current interference. It can be seen that it does not represent the net current effective value. Therefore, when measuring the effective current value, it is necessary to calculate the effective value by excluding the first term in the square root of the right side of [Formula 10].

However, as shown in FIG. 19, a conventional main electrode current effective value calculation circuit 28 ′ includes a multiplier 29 that squares an instantaneous current value i ₁ , and an integrator that integrates the operation result of the multiplier 29. 30, a root calculator 31 for obtaining the square root of the calculation result in the integrator 30, and a hold circuit 32 for holding the calculation result in the root calculator 31. Similarly, the conventional bottom electrode current effective value calculation circuit 33 'squares the instantaneous current value i ₂ , and the calculation result of the multiplier 34. Are integrated, a root calculator 36 for obtaining the square root of the calculation result in the integrator 35, and a hold circuit 37 for holding the calculation result in the root calculator 36. The net current actually It was not possible to determine the value. Since the integration in the integrators 30 and 35 is reset every period, hold circuits 32 and 37 are provided.

  Furthermore, the circuit scheme of FIG. 13 will be considered below for the calculation of the effective power value.

）が炉内抵抗で分圧され、非通電側のトランス（８又は１１）の二次コイル側端子にも印加された状態となる。非通電側のトランス（８又は１１）の一次コイル側に接続されているサイリスタ（１０又は１３）は消弧状態にあるため、二次コイル側電圧からみると開放（無負荷）状態にある。これによってトランス（８又は１１）の二次コイル側回路に励磁電流が流れる。 Since the main electrode power source 9 and the bottom electrode power source 12 are controlled separately (in accordance with their respective purposes), generally α ≠ β, and only one of them is energized. At this time, the electrical circuit on the non-energized side is always in a conductive state between the secondary coil side of the transformer (8 or 11) and the electrode (5 or 6). For this reason, the voltage on the energization side (in the example of FIG.

) Is divided by the resistance in the furnace and applied to the secondary coil side terminal of the non-energized transformer (8 or 11). Since the thyristor (10 or 13) connected to the primary coil side of the non-energized transformer (8 or 11) is in an arc extinguishing state, it is in an open (no load) state when viewed from the secondary coil side voltage. As a result, an exciting current flows through the secondary coil side circuit of the transformer (8 or 11).

  In an ideal transformer, even if an exciting current flows, it is reactive power. Therefore, the active power control is not affected. However, in an actual circuit, a loss due to winding resistance, cable resistance, etc. occurs (although it is very small) and is added to the effective power meter effective value calculation on the non-energized side. This is called power interference.

  This power interference not only affects the effective power effective value calculation on the non-energized side on the energized side, but also indicates that the power corresponding to the power interference among the active power on the energized side is a loss outside the electric melting furnace. Also means. Therefore, when strict electric melting furnace power control is to be performed, it is necessary to grasp the effective electric power outside the electric melting furnace consumed on the non-energized side.

From the [Expression 5] and [Expression 9], the measured instantaneous power is expressed by the following expression.

Therefore, the measured power effective value is expressed as follows.

  Here, the first term on the right side means power interference on the energized side measured on the non-energized side. This also means the lost power consumed outside the electric melting furnace from the energization side.

On the other hand, the net effective power value energized by the main electrode power source 9 and the bottom electrode power source 12 should be given by the following equation.

  Comparing [Equation 14], which is actually measured and calculated, with the ideal [Equation 15], the first term on the right side of [Equation 14] does not match [Equation 15] due to power interference. It can be seen that the effective power value is not represented. Therefore, when measuring the power effective value, it is necessary to calculate the effective value by excluding the first term on the right side of the equation [14].

However, as shown in FIG. 21, the conventional main electrode power effective value calculation circuit 38 'outputs the instantaneous value of power by multiplying the instantaneous value v ₁ of the voltage between the main electrodes 5 and the instantaneous value i _{1 of the} current. A multiplier 39, an integrator 40 that integrates an instantaneous value of the power output from the multiplier 39, and a hold circuit 41 that holds a calculation result in the integrator 40. Therefore, the net effective power value cannot be obtained, and similarly, the conventional bottom electrode power effective value calculation circuit 42 ′ has an instantaneous voltage v between the bottom electrode 6 and one of the main electrodes 5. ₂ is multiplied by the instantaneous current value i ₂ to output an instantaneous power value, an integrator 44 for integrating the instantaneous power value output from the multiplier 43, and an operation performed by the integrator 44. And a hold circuit 45 for holding the result. , It has not been possible to obtain the effective value of power of the net. Since the integration in the integrators 40 and 44 is reset every cycle, hold circuits 41 and 45 are provided.

  On the other hand, the circuit method of FIGS. 14 and 13 will be considered below regarding the measurement positions of voltage, current, and power.

  As shown in FIG. 22, the conventional power supply control panel is installed at a position away from the melting furnace body 3 for convenience and convenience of panel manufacture, and includes a main electrode voltmeter 14 as a voltage measuring unit, a bottom electrode, and the like. The main electrode ammeter 15 and the bottom electrode voltmeter 16 as a current measuring unit and the bottom electrode voltmeter 16 are provided in a measurement control unit inside the power supply control panel. However, in such a case, electric melting furnaces that handle low-resistance materials such as glass tend to have low voltage and large current, and cable resistance such as power cables and bus bars laid from the power supply control panel to the electric melting furnace. Voltage drop due to contact resistance and power loss are insignificant. For this reason, it is necessary to exclude the voltage drop and the power loss due to the cable in order to more meaningfully calculate the effective values of voltage, current, and power.

  Solving the above problems means that the circuit system shown in FIG. 13 can be employed without any practical problems without depending on FIG. 14, and the problems left by the electric melting furnace shown in FIG. 14 are also solved. Therefore, the present inventor has found that both FIG. 14 and FIG. 13 can be selected equally according to the load characteristics required for each target plant.

  In view of such circumstances, the present invention can accurately grasp each effective value of voltage, current, and power, can improve the controllability of operation, and increases the degree of freedom of the location of the switching element in the electric circuit, An object of the present invention is to provide an electric melting furnace capable of flexibly responding to individual requirements that differ from plant to plant as well as cost reduction.

In the present invention, a melting furnace main body having a flow-down port formed at the bottom, and a material to be melted in the melting furnace main body are heated by being energized between the melting furnace main body and an intermediate portion in the vertical direction of the inner wall of the melting furnace main body. A pair of main electrodes to be melted, a bottom electrode disposed at the bottom of the melting furnace body and energized between one of the main electrodes to heat and melt a material to be melted at the bottom of the melting furnace body; Main electrode power source having a main electrode transformer for energizing between electrodes, and main electrode switching provided on either the primary coil side or the secondary coil side of the main electrode transformer of the main electrode power source A power source for a bottom electrode having a transformer for a bottom electrode for energizing between the element and one of the bottom electrode and the main electrode, and a primary coil side or a secondary coil side of the bottom electrode transformer of the bottom electrode power source Provided in either one of Was made and a bottom electrode for the switching element in an electric melting furnace,
A main electrode ignition state determination circuit for determining whether the main electrode switching element is in an ignition state or an extinguishing state;
Based on information from the main electrode ignition state determination circuit, the main electrode voltage is obtained by obtaining the effective value of the voltage from the instantaneous value of the voltage between the main electrodes and outputting it only while the main electrode switching element is in the ignition state. An effective value calculation circuit;
A bottom electrode ignition state determination circuit for determining whether the bottom electrode switching element is in an ignition state or an extinguishing state; and
Based on the information from the bottom electrode ignition state determination circuit, the effective value of the voltage is obtained from the instantaneous value of the voltage between the bottom electrode and one of the main electrodes only while the bottom electrode switching element is in the ignition state. And an output voltage effective value calculation circuit for the bottom electrode that outputs the output of the electric melting furnace.

  According to the above means, the following operation can be obtained.

  In the main electrode voltage effective value calculation circuit, based on the information from the main electrode ignition state determination circuit, the effective value of the voltage is determined from the instantaneous value of the voltage between the main electrodes only while the main electrode switching element is in the ignition state. Since the value is obtained and output, it is possible to obtain the net effective voltage value, and in the bottom electrode voltage effective value calculation circuit, the bottom electrode is based on the information from the bottom electrode ignition state determination circuit. Since the effective value of the voltage is obtained and output from the instantaneous value of the voltage between the bottom electrode and one of the main electrodes only while the switching device is in the ignition state, the net effective voltage value can be obtained. This makes it possible to improve the controllability of the operation, increase the degree of freedom in the arrangement of the main electrode switching element and the bottom electrode switching element in the electric circuit, and not only reduce costs but also plan. Also flexibly adaptable to the individual requirements different for each.

The present invention also provides a melting furnace main body having a flow-down port formed at the bottom, and an object to be melted in the melting furnace main body that is disposed opposite to an intermediate portion in the vertical direction of the inner wall of the melting furnace main body and is energized between them. A pair of main electrodes to be heated and melted, and a bottom electrode which is arranged at the bottom of the melting furnace body and heats and melts the material to be melted in the bottom of the melting furnace body by energization between one of the main electrodes; A main electrode power source having a main electrode transformer for energizing between the main electrodes, and a main electrode provided on either the primary coil side or the secondary coil side of the main electrode transformer of the main electrode power source Power source for a bottom electrode having a transformer for a switching element, a bottom electrode transformer for energizing between one of the bottom electrode and the main electrode, and a primary coil side or a secondary of the bottom electrode transformer of the bottom electrode power source Installed on either side of coil In electric melting furnace comprising a was a bottom electrode for the switching element,
A main electrode ignition state determination circuit for determining whether the main electrode switching element is in an ignition state or an extinguishing state;
Based on the information from the main electrode ignition state determination circuit, the main electrode current is obtained by obtaining the effective value of the current from the instantaneous value of the current between the main electrodes and outputting it only while the main electrode switching element is in the ignition state. An effective value calculation circuit;
A bottom electrode ignition state determination circuit for determining whether the bottom electrode switching element is in an ignition state or an extinguishing state; and
Based on the information from the bottom electrode ignition state determination circuit, the effective value of the current is obtained from the instantaneous value of the current between the bottom electrode and one of the main electrodes only while the bottom electrode switching element is in the ignition state. And an electric current effective value calculation circuit for the bottom electrode that outputs the current.

  According to the above means, the following operation can be obtained.

  In the main electrode current effective value calculation circuit, based on the information from the main electrode ignition state determination circuit, the current effective value is calculated from the instantaneous value of the current between the main electrodes only while the main electrode switching element is in the ignition state. Since the value is obtained and output, it is possible to obtain the net current effective value, and in the bottom electrode current effective value calculation circuit, the bottom electrode is based on the information from the bottom electrode ignition state determination circuit. Since the effective value of the current is obtained and output from the instantaneous value of the current between the bottom electrode and one of the main electrodes only while the switching element is in the ignition state, the net effective current value can be obtained. This makes it possible to improve the controllability of the operation, increase the degree of freedom in the arrangement of the main electrode switching element and the bottom electrode switching element in the electric circuit, and not only reduce costs but also plan. Also flexibly adaptable to the individual requirements different for each.

The present invention also provides a melting furnace main body having a flow-down port formed at the bottom, and an object to be melted in the melting furnace main body that is disposed opposite to an intermediate portion in the vertical direction of the inner wall of the melting furnace main body and is energized between them. A pair of main electrodes to be heated and melted, and a bottom electrode which is arranged at the bottom of the melting furnace body and heats and melts the material to be melted in the bottom of the melting furnace body by energization between one of the main electrodes; A main electrode power source having a main electrode transformer for energizing between the main electrodes, and a main electrode provided on either the primary coil side or the secondary coil side of the main electrode transformer of the main electrode power source Power source for a bottom electrode having a transformer for a switching element, a bottom electrode transformer for energizing between one of the bottom electrode and the main electrode, and a primary coil side or a secondary of the bottom electrode transformer of the bottom electrode power source Installed on either side of coil In electric melting furnace comprising a was a bottom electrode for the switching element,
A main electrode ignition state determination circuit for determining whether the main electrode switching element is in an ignition state or an extinguishing state;
Based on the information from the main electrode ignition state determination circuit, the power between the main electrodes is determined from the instantaneous value of the voltage between the main electrodes and the instantaneous value of the current between the main electrodes only while the switching element for the main electrode is in the ignition state. Power effective value calculation circuit for the main electrode that calculates and outputs the effective value of
A bottom electrode ignition state determination circuit for determining whether the bottom electrode switching element is in an ignition state or an extinguishing state; and
Based on the information from the bottom electrode firing state determination circuit, the instantaneous value of the voltage between the bottom electrode and one of the main electrodes and one of the bottom electrode and the main electrode only while the bottom electrode switching element is in the firing state. An electric melting furnace comprising a bottom electrode power RMS value calculation circuit that calculates and outputs an effective value of power between the bottom electrode and one of the main electrodes from an instantaneous current value between the bottom electrode and the main electrode. It is such a thing.

  According to the above means, the following operation can be obtained.

  In the main electrode power effective value calculation circuit, based on the information from the main electrode ignition state determination circuit, the instantaneous value of the voltage between the main electrodes and between the main electrodes only while the main electrode switching element is in the ignition state. Since the effective value of the power between the main electrodes is obtained and output from the instantaneous value of the current, it is possible to determine the net effective power value, and in the bottom electrode power effective value calculation circuit, Based on the information from the ignition state determination circuit, the instantaneous value of the voltage between the bottom electrode and one of the main electrodes and between the bottom electrode and one of the main electrodes only while the switching element for the bottom electrode is in the ignition state. Since the effective value of the electric power between the bottom electrode and the main electrode is obtained from the instantaneous value of the current and output, the net effective electric power value can be obtained, the controllability of the operation is improved, and the electric power is improved. Switch for main electrode in circuit Also increases the degree of freedom of arrangement positions of the ring element and the bottom electrode for the switching element, not only the cost can be reduced, it is flexibly adaptable to different individual requirements for each plant.

The present invention also provides a melting furnace main body having a flow-down port formed at the bottom, and an object to be melted in the melting furnace main body that is disposed opposite to an intermediate portion in the vertical direction of the inner wall of the melting furnace main body and is energized between them. A pair of main electrodes to be heated and melted, and a bottom electrode which is arranged at the bottom of the melting furnace body and heats and melts the material to be melted in the bottom of the melting furnace body by energization between one of the main electrodes; A main electrode power source having a main electrode transformer for energizing between the main electrodes, and a main electrode provided on either the primary coil side or the secondary coil side of the main electrode transformer of the main electrode power source Power source for a bottom electrode having a transformer for a switching element, a bottom electrode transformer for energizing between one of the bottom electrode and the main electrode, and a primary coil side or a secondary of the bottom electrode transformer of the bottom electrode power source Installed on either side of coil In electric melting furnace comprising a was a bottom electrode for the switching element,
A main electrode ignition state determination circuit for determining whether the main electrode switching element is in an ignition state or an extinguishing state;
A bottom electrode ignition state determination circuit for determining whether the bottom electrode switching element is in an ignition state or an extinguishing state; and
Based on the information from the main electrode ignition state determination circuit, the power between the main electrodes is determined from the instantaneous value of the voltage between the main electrodes and the instantaneous value of the current between the main electrodes only while the switching element for the main electrode is in the ignition state. And the main electrode switching element is in an ignition state and the bottom electrode switching element is extinguished based on information from the main electrode ignition state determination circuit and the bottom electrode ignition state determination circuit. The power of the power between the bottom electrode and one of the main electrodes is determined from the instantaneous value of the voltage between the bottom electrode and one of the main electrodes and the instantaneous value of the current between the bottom electrode and one of the main electrodes only while in the state. An instantaneous value is obtained, and an effective value of the power between the main electrodes is obtained and output based on a value obtained by subtracting the instantaneous value of the power between the bottom electrode and one of the main electrodes from the instantaneous value of the power between the main electrodes. A power effective value calculation circuit for the main electrode,
Based on the information from the bottom electrode ignition state determination circuit, the instantaneous value of the voltage between the bottom electrode and one of the main electrodes and one of the bottom electrode and the main electrode only while the bottom electrode switching element is in the ignition state. The instantaneous value of the electric power between the bottom electrode and one of the main electrodes is obtained from the instantaneous value of the current between the main electrode and the information from the main electrode ignition state determination circuit and the bottom electrode ignition state determination circuit. Based on the instantaneous value of the voltage between the main electrodes and the instantaneous value of the current between the main electrodes, only when the bottom electrode switching element is in the ignition state and the main electrode switching element is in the arc extinguishing state, An instantaneous value is obtained, and the electric power between the bottom electrode and one of the main electrodes is obtained by subtracting the instantaneous value of the electric power between the main electrodes from the instantaneous value of the electric power between the bottom electrode and the main electrode. For the bottom electrode that calculates and outputs the effective value of In which according to the electric melting furnace, characterized in that a effective value calculating circuit.

  According to the above means, the following operation can be obtained.

  In the main electrode power effective value calculation circuit, based on the information from the main electrode ignition state determination circuit, the instantaneous value of the voltage between the main electrodes and between the main electrodes only while the main electrode switching element is in the ignition state. The instantaneous value of the power between the main electrodes is obtained from the instantaneous value of the current, and the switching element for the main electrode is ignited based on the information from the ignition state determination circuit for the main electrode and the ignition state determination circuit for the bottom electrode. The bottom electrode from the instantaneous value of the voltage between the bottom electrode and one of the main electrodes and the instantaneous value of the current between the bottom electrode and one of the main electrodes only while the switching element for the bottom electrode is in the arc extinguishing state An instantaneous value of power between the main electrode and one of the main electrodes is obtained, based on a value obtained by subtracting an instantaneous value of power between the bottom electrode and one of the main electrodes from the instantaneous value of power between the main electrodes The effective value of power between the main electrodes is obtained. To be outputted, we are possible to obtain the effective value of power of the net consumed in an electric furnace more accurately. In the bottom electrode power effective value calculation circuit, the voltage between the bottom electrode and one of the main electrodes is calculated only while the bottom electrode switching element is in the ignition state based on the information from the bottom electrode ignition state determination circuit. An instantaneous value of power between the bottom electrode and one of the main electrodes is obtained from the instantaneous value and an instantaneous value of the current between the bottom electrode and the main electrode, and the ignition state determination circuit for the main electrode and the bottom Based on the information from the electrode ignition state determination circuit, the instantaneous value of the voltage between the main electrodes and between the main electrodes only when the bottom electrode switching element is in the ignition state and the main electrode switching element is in the arc extinguishing state. Based on the value obtained by subtracting the instantaneous value of the electric power between the main electrodes from the instantaneous value of the electric power between the bottom electrode and one of the main electrodes. Between the bottom electrode and one of the main electrodes Since the effective value of the power is obtained and output, it is possible to obtain the effective value of power of the net consumed in an electric furnace more accurately. As a result, the controllability of the operation is improved, the degree of freedom of the arrangement location of the main electrode switching element and the bottom electrode switching element in the electric circuit is increased, and not only the cost can be reduced, but also different individual plants. It is possible to respond flexibly to requests.

In the electric melting furnace, each of the main electrode switching element and the bottom electrode switching element is a self-excited element capable of arbitrarily controlling the ON / OFF timing,
Each of the main electrode ignition state determination circuit and the bottom electrode ignition state determination circuit is configured to determine the ignition state of the self-excited element based on a gate signal output from the gate control circuit of the self-excited element. can do.

In the electric melting furnace, each of the switching element for the main electrode and the switching element for the bottom electrode is a separately excited element that can arbitrarily control the ON timing but cannot control the OFF timing,
The main electrode ignition state determination circuit and the bottom electrode ignition state determination circuit each determine a voltage difference before and after a separately excited element that is in an ignition state by an ignition signal output from the ignition circuit. When the voltage difference is V _L or less and it is determined that the separately excited element is in an ignition state, and the voltage difference is V _H or more and the forward voltage drop is large, the separately excited element is in an arc extinguished state. It can also be configured to determine.

In the electric melting furnace, each of the switching element for the main electrode and the switching element for the bottom electrode is a separately excited element that can arbitrarily control the ON timing but cannot control the OFF timing,
The main electrode firing state determination circuit and the bottom electrode firing state determination circuit each set a single flip-flop by the firing signal output from the firing circuit of the separately excited element, and the separately excited element is in the firing state. The voltage difference before and after the separately excited element that is in the ignition state is detected by the voltage difference determination circuit based on the ignition signal output from the ignition circuit, and the forward voltage is detected when the voltage difference is V _H or more. When the drop is large, the single flip-flop may be reset to determine that the separately excited element is in the arc extinguishing state.

In the electric melting furnace, each of the switching element for the main electrode and the switching element for the bottom electrode is a separately excited element that can arbitrarily control the ON timing but cannot control the OFF timing,
The main electrode ignition state determination circuit and the bottom electrode ignition state determination circuit each detect a holding current of a separately excited element that is in an ignition state based on an ignition signal output from the ignition circuit, by a current value determination circuit. The holding current is not more than I _L and it is determined that the separately excited element is in an ignition state, and the holding current is not less than I _H and it is determined that the separately excited element is in an extinguished state.

In the electric melting furnace, each of the switching element for the main electrode and the switching element for the bottom electrode is a separately excited element that can arbitrarily control the ON timing but cannot control the OFF timing,
The main electrode firing state determination circuit and the bottom electrode firing state determination circuit each set a single flip-flop by the firing signal output from the firing circuit of the separately excited element, and the separately excited element is in the firing state. It determines that the said single flip-flop at said point by firing signal outputted from the firing circuit detects the holding current of the separately excited element to be firing state by the current value determination circuit, the holding current I _H or Can be configured to determine that the separately excited element is in the arc extinguishing state.

  In the electric melting furnace, at least the voltage and the current between the main electrodes are detected from the main electrode itself or the vicinity of the main electrode, and at least the voltage and the current between the bottom electrode and one of the main electrodes are detected. It is effective to configure to detect from the bottom electrode itself or from the immediate vicinity of the bottom electrode.

  According to the electric melting furnace of the present invention, it is possible to accurately grasp each effective value of voltage, current, and power, to improve the controllability of operation, and to increase the degree of freedom of the location of the switching element in the electric circuit, In addition to cost reduction, it is possible to achieve an excellent effect of being able to flexibly respond to individual requests that differ from plant to plant.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a main electrode voltage effective value calculation circuit 18 and a bottom electrode voltage effective value calculation circuit 23 in an example of an embodiment of the present invention. In the figure, the same reference numerals as those in FIG. The parts represent the same thing, and the basic configuration is the same as the conventional one shown in FIG. 17, but the feature of this illustrated example is as shown in FIG.
A main electrode ignition state determination circuit 46 for determining whether the main electrode switching element is in an ignition state or an extinguishing state is provided, and based on information from the main electrode ignition state determination circuit 46 Only when the main electrode switching element is in the ignition state, a switch 47 for switching to the a side and outputting an instantaneous value of the voltage between the main electrodes 5 is provided on the input side of the multiplier 19 to provide a voltage effective value for the main electrode. While configuring the calculation circuit 18,
A bottom electrode ignition state determination circuit 48 for determining whether the bottom electrode switching element is in an ignition state or an arc extinction state is provided, and based on information from the bottom electrode ignition state determination circuit 48 A switch 49 that switches to the a side and outputs an instantaneous value of the voltage between the bottom electrode 6 and one of the main electrodes 5 is provided on the input side of the multiplier 24 while the switching element for the bottom electrode is in the ignition state. The bottom electrode voltage effective value calculation circuit 23 is provided.

  The switch 47 is switched to the b side and outputs 0 (zero) while the main electrode switching element is in the extinguishing state based on the information from the main electrode ignition state determination circuit 46. The switch 49 is switched to the b side and outputs 0 (zero) while the bottom electrode switching element is in the arc extinguishing state based on the information from the bottom electrode ignition state determination circuit 48. Yes.

  As the main electrode switching element and the bottom electrode switching element, self-excited elements capable of arbitrarily controlling the ON / OFF timing (for example, IGBT: insulated gate bipolar transistor, GTO: gate turn-off thyristor, MOSFET: field effect transistor, etc.) Alternatively, any other excitation type element (for example, thyristor) that can control the ON timing arbitrarily but cannot control the OFF timing can be used. 13 and 14 show an example in which thyristors 10 and 13 are used as the main electrode switching element and the bottom electrode switching element.

  When a self-excited element such as IGBT is used as the main electrode switching element and the bottom electrode switching element, the main electrode ignition state determination circuit 46 and the bottom electrode ignition state determination circuit 48 are respectively As shown in FIG. 2, the ignition state of the self-excited element can be determined based on the gate signal 51 output from the gate control circuit 50 of the self-excited element.

When separately excited elements such as thyristors are used as the main electrode switching element and the bottom electrode switching element, the main electrode ignition state determination circuit 46 and the bottom electrode ignition state determination circuit 48 are respectively shown in FIG. As shown in FIG. 4, the voltage difference determination circuit 54 detects the voltage difference before and after the separately-excited element that is in the ignition state by the ignition signal 53 output from the ignition circuit 52, and the voltage difference is a positive value. It is determined that the separately excited element is in an ignition state at a voltage threshold value V _L that is slightly larger than the forward voltage drop, and it is determined that the separately excited element is in an extinguished state if the voltage difference is a negative value or greater than V _L. Can be configured to.

  When a separately excited element such as a thyristor is used as the main electrode switching element and the bottom electrode switching element, the main electrode ignition state determination circuit 46 and the bottom electrode ignition state determination circuit 48 are respectively As shown in FIG. 4, the single flip-flop 55 is set by the ignition signal 53 output from the ignition circuit 52 of the separately excited element, and it is determined that the separately excited element is in the ignition state. A voltage difference determination circuit 54 detects a voltage difference before and after the separately excited element that is in an ignition state based on the output ignition signal 53, and resets the single flip-flop 55 when the voltage difference is a negative value, thereby separately exciting the voltage. It can also be configured to determine that the element is in an arc extinguishing state.

Furthermore, when a separately excited element such as a thyristor is used as the main electrode switching element and the bottom electrode switching element, the main electrode ignition state determination circuit 46 and the bottom electrode ignition state determination circuit 48 are respectively As shown in FIG. 5, the current of the separately excited element that is in the ignition state is detected by the current value determination circuit 56 based on the ignition signal 53 output from the ignition circuit 52, and the current is slightly smaller than the holding current of the element. as the separately excited elements at a large current threshold I _H or is determined to be in the firing state, the current separately excited elements at slightly below lower current threshold I _L than the holding current of the device is determined to be in extinguishing state It can also be configured.

When a separately excited element such as a thyristor is used as the main electrode switching element and the bottom electrode switching element, the main electrode ignition state determination circuit 46 and the bottom electrode ignition state determination circuit 48 are respectively As shown in FIG. 6, the single flip-flop 57 is set by the ignition signal 53 output from the ignition circuit 52 of the separately excited element, and it is determined that the separately excited element is in the ignition state. detecting a current of the separately excited element by firing signal 53 that is output the firing state by the current value determination circuit 56, the single flip-flop 57 said current is below slightly smaller current threshold I _L than the holding current of the element Can be configured to determine that the separately excited element is in the arc extinguishing state.

  Next, the operation of the illustrated example will be described.

  In the main electrode voltage effective value calculation circuit 18, the switch 47 is switched to the a side only while the main electrode switching element is in the ignition state based on the information from the main electrode ignition state determination circuit 46. The effective value of the voltage is obtained from the instantaneous value of the voltage between 5 and output, and while the switching element 47 is switched to the b side while the main electrode switching element is in the arc extinction state, the effective voltage value is calculated. It becomes a part to be excluded (see FIG. 7). Similarly, in the bottom electrode voltage effective value calculation circuit 23, the switch 49 is switched to the a side only while the bottom electrode switching element is in the ignition state based on the information from the bottom electrode ignition state determination circuit 48. The effective value of the voltage is obtained from the instantaneous value of the voltage between the bottom electrode and one of the main electrodes 5 and output, and the switching element 49 is switched to the b side when the bottom electrode switching element is in the arc extinguishing state. While this is done, it is excluded from the voltage RMS calculation. For this reason, the first term in the square root of the right side of the [Expression 6] is eliminated, and the ideal voltage effective value of the [Expression 7] is calculated, and the net effective voltage value can be obtained for each. Note that the arc extinguishing timing may be delayed from the ideal timing T due to the inductance of the circuit and may shift to the next cycle. Even in such a case, the circuit can calculate the net effective voltage value.

  As a result, the controllability of the operation of the electric melting furnace is improved, the degree of freedom of arrangement of the main electrode switching element and the bottom electrode switching element in the electric circuit is increased, and the object to be melted such as glass having a very low current resistance. On the other hand, in an electric melting furnace that requires energization control with a low voltage and a large current, expensive switching elements such as thyristors 10 and 13 are arranged on the high voltage and small current side of the transformers 8 and 11 (see FIG. 13). The rated current capacity can be set and designed lower than when a switching element is installed on the low voltage / large current side (see FIG. 14), which has the merit of leading to a significant cost reduction of the device. On the contrary, it is possible to select the installation of the transformers 8 and 11 on the low voltage side as necessary from the viewpoint of the withstand voltage of the switching element, and it is possible to flexibly respond to individual requests that differ from plant to plant.

  In this way, the effective voltage value can be accurately grasped, the controllability of operation can be improved, the degree of freedom of the arrangement of the switching elements in the electric circuit is increased, and not only the cost is reduced, but also individual requirements that differ from plant to plant. Can respond flexibly.

FIG. 8 shows the current effective value calculation circuit 28 for the main electrode and the current effective value calculation circuit 33 for the bottom electrode in an example of the embodiment of the present invention, and the same reference numerals as those in FIG. The parts represent the same, and the basic configuration is the same as the conventional one shown in FIG. 19, but the feature of this example is that the switching element for the main electrode is a point as shown in FIG. A main electrode ignition state determination circuit 46 for determining whether the arc state or the arc extinguishing state is present is provided. Based on the information from the main electrode ignition state determination circuit 46, the main electrode switching element is turned on. A switch 58 that outputs the instantaneous value of the current between the main electrodes 5 and outputs the instantaneous value of the current between the main electrodes 5 is provided on the input side of the multiplier 29 to constitute the main electrode current effective value calculation circuit 28 while being in the arc state. ,
A bottom electrode ignition state determination circuit 48 for determining whether the bottom electrode switching element is in an ignition state or an arc extinction state is provided, and based on information from the bottom electrode ignition state determination circuit 48 A switch 59 that outputs the instantaneous value of the current between the bottom electrode 6 and one of the main electrodes 5 is switched to the input side of the multiplier 34 while the bottom electrode switching element is in the ignition state. The bottom electrode current effective value calculation circuit 33 is provided.

  The switch 58 is switched to the b side and outputs 0 (zero) while the main electrode switching element is in the arc extinguishing state based on the information from the main electrode ignition state determination circuit 46. The switch 59 is switched to the b side and outputs 0 (zero) while the bottom electrode switching element is in the arc extinguishing state based on the information from the bottom electrode ignition state determination circuit 48. Yes.

  When a self-excited element such as IGBT is used as the main electrode switching element and the bottom electrode switching element, the main electrode ignition state determination circuit 46 and the bottom electrode ignition state determination circuit 48 are respectively As in the case of the main electrode voltage effective value calculation circuit 18 and the bottom electrode voltage effective value calculation circuit 23, the configuration shown in FIG.

  When separately excited elements such as thyristors are used as the main electrode switching element and the bottom electrode switching element, the main electrode ignition state determination circuit 46 and the bottom electrode ignition state determination circuit 48 are respectively As in the case of the electrode voltage effective value calculation circuit 18 and the bottom electrode voltage effective value calculation circuit 23, the configuration shown in any of FIGS. 3, 4, 5, and 6 can be employed.

  Next, the operation of the example shown in FIG. 8 will be described.

  In the main electrode current effective value calculation circuit 28, the switch 58 is switched to the a side only while the main electrode switching element is in the ignition state based on the information from the main electrode ignition state determination circuit 46. The effective value of the current is obtained and output from the instantaneous value of the current between 5, and the current effective value calculation is performed while the main electrode switching element is in the arc extinguishing state and the switch 58 is switched to the b side. It will be an excluded part. Similarly, in the bottom electrode current effective value calculation circuit 33, the switch 59 switches to the a side only while the bottom electrode switching element is in the ignition state based on the information from the bottom electrode ignition state determination circuit 48. The effective value of the current is obtained and output from the instantaneous value of the current between the bottom electrode and one of the main electrodes 5, and the switching element 59 is switched to the b side when the bottom electrode switching element is in the arc extinguishing state. While this is being done, it will be excluded from the calculation of the RMS current value. For this reason, the first current term in the square root of the right side of the equation [6] is eliminated to calculate the ideal current effective value of the equation [7], and it is possible to obtain the net current effective value. Note that the arc extinguishing timing may be delayed from the ideal timing T due to the inductance of the circuit and may shift to the next cycle. Even in such a case, the circuit can calculate the net effective current value.

  As a result, the controllability of the operation of the electric melting furnace is improved, the degree of freedom of arrangement of the main electrode switching element and the bottom electrode switching element in the electric circuit is increased, and the object to be melted such as glass having a very low current resistance. On the other hand, in an electric melting furnace that requires energization control with a low voltage and a large current, expensive switching elements such as thyristors 10 and 13 are arranged on the high voltage and small current side of the transformers 8 and 11 (see FIG. 13). The rated current capacity can be set and designed lower than when a switching element is installed on the low voltage / large current side (see FIG. 14), which has the merit of leading to a significant cost reduction of the device. On the contrary, it is possible to select the installation of the transformers 8 and 11 on the low voltage side as necessary from the viewpoint of the withstand voltage of the switching element, and it is possible to flexibly respond to individual requests that differ from plant to plant.

  In this way, the effective current value can be accurately grasped, the controllability of operation can be improved, the degree of freedom of the arrangement of the switching elements in the electric circuit is increased, and not only costs are reduced, but also individual requirements that differ from plant to plant. Can respond flexibly.

FIG. 9 shows a main electrode power effective value calculation circuit 38 and a bottom electrode power effective value calculation circuit 42 in an example of an embodiment of the present invention, and the same reference numerals as those in FIG. The parts represent the same, and the basic configuration is the same as the conventional one shown in FIG. 21, but the feature of this example is that the switching element for the main electrode is a point as shown in FIG. A main electrode ignition state determination circuit 46 for determining whether the arc state or the arc extinguishing state is present is provided. Based on the information from the main electrode ignition state determination circuit 46, the main electrode switching element is turned on. A switch 60 is provided between the multiplier 39 and the integrator 40 to switch to the a side and output the instantaneous value of the power between the main electrodes 5 only during the arc state, and the main electrode power effective value calculation circuit 38 is provided. As well as
A bottom electrode ignition state determination circuit 48 for determining whether the bottom electrode switching element is in an ignition state or an arc extinction state is provided, and based on information from the bottom electrode ignition state determination circuit 48 Only when the switching element for the bottom electrode is in the ignition state, the switching device 61 is switched to the a side and outputs an instantaneous value of power between the bottom electrode 6 and one of the main electrodes 5. The bottom electrode power rms value calculation circuit 42 is provided.

  The switch 60 is switched to the b side and outputs 0 (zero) while the main electrode switching element is in the arc extinguishing state based on the information from the main electrode ignition state determination circuit 46. The switch 61 is switched to the b side and outputs 0 (zero) while the bottom electrode switching element is in the arc extinguishing state based on the information from the bottom electrode ignition state determination circuit 48. Yes.

  When a self-excited element such as IGBT is used as the main electrode switching element and the bottom electrode switching element, the main electrode ignition state determination circuit 46 and the bottom electrode ignition state determination circuit 48 are respectively As in the case of the main electrode voltage effective value calculation circuit 18 and the bottom electrode voltage effective value calculation circuit 23, the configuration shown in FIG.

  When separately excited elements such as thyristors are used as the main electrode switching element and the bottom electrode switching element, the main electrode ignition state determination circuit 46 and the bottom electrode ignition state determination circuit 48 are respectively As in the case of the electrode voltage effective value calculation circuit 18 and the bottom electrode voltage effective value calculation circuit 23, the configuration shown in any of FIGS. 3, 4, 5, and 6 can be employed.

  Next, the operation of the example shown in FIG. 9 will be described.

  In the main electrode power effective value calculation circuit 38, the switch 60 is switched to the a side only while the main electrode switching element is in the ignition state based on the information from the main electrode ignition state determination circuit 46. The effective value of the electric power is obtained from the instantaneous value of the electric power between 5 and output, and while the switching element for the main electrode is in the arc extinguishing state and the switcher 60 is switched to the b side, the effective electric power value is calculated. It will be an excluded part. Similarly, in the bottom electrode power effective value calculation circuit 42, the switch 61 switches to the a side only while the bottom electrode switching element is in the ignition state based on the information from the bottom electrode ignition state determination circuit 48. The effective value of the electric power is obtained from the instantaneous value of the electric power between the bottom electrode 6 and one of the main electrodes 5 and output. The bottom electrode switching element is in the arc extinguishing state and the switch 61 is moved to the b side. While switching, it is a part excluded from the calculation of the effective power value. For this reason, the first term on the right side of the formula [14] is eliminated, and the ideal power effective value of the formula [15] is calculated, and the net power effective value can be obtained for each. Note that the arc extinguishing timing may be delayed from the ideal timing T due to the inductance of the circuit, and may shift to the next cycle. Even in such a case, the present circuit can calculate the net effective power value.

  As a result, the controllability of the operation of the electric melting furnace is improved, the degree of freedom of arrangement of the main electrode switching element and the bottom electrode switching element in the electric circuit is increased, and the object to be melted such as glass having a very low current resistance. On the other hand, in an electric melting furnace that requires energization control with a low voltage and a large current, expensive switching elements such as thyristors 10 and 13 are arranged on the high voltage and small current side of the transformers 8 and 11 (see FIG. 13). The rated current capacity can be set and designed lower than when a switching element is installed on the low voltage / large current side (see FIG. 14), which has the merit of leading to a significant cost reduction of the device. On the contrary, it is possible to select the installation of the transformers 8 and 11 on the low voltage side as necessary from the viewpoint of the withstand voltage of the switching element, and it is possible to flexibly respond to individual requests that differ from plant to plant.

  In this way, it is possible to accurately grasp the effective power value, improve the controllability of the operation, increase the degree of freedom of the location of the switching elements in the electric circuit, and not only reduce costs but also individual requirements that differ from plant to plant. Can respond flexibly.

FIG. 10 shows a modification of the main electrode power effective value calculation circuit 38 and the bottom electrode power effective value calculation circuit 42 in the example of the embodiment of the present invention. The parts marked with are the same, and the basic configuration is the same as that shown in FIG. 9, but the feature of this example is that the bottom electrode 6 and the main electrode are shown in FIG. 5, a multiplier 43 ′ that multiplies the instantaneous voltage value v ₂ and the instantaneous current value i ₂ to output an instantaneous power value, a main electrode ignition state determination circuit 46, and a bottom electrode point. Based on the information from the arc state determination circuit 48, the bottom part output from the multiplier 43 'is switched to the c side only while the main electrode switching element is in the ignition state and the bottom electrode switching element is in the arc extinguishing state. The instantaneous value of the voltage between the electrode 6 and one of the main electrodes 5 The bottom electrode output from the multiplier 43 'via the switch 61' based on the instantaneous power value between the main electrode 5 output from the multiplier 39 via the switch 60. 6 and a subtractor 62 that outputs a value obtained by subtracting the instantaneous value of power between one of the main electrodes 5 and the integrator 40 to the integrator 40. Based on the information from the main electrode ignition state determination circuit 46, the main electrode 5 is obtained from the instantaneous value of the voltage between the main electrodes 5 and the instantaneous value of the current between the main electrodes 5 only while the switching element for main electrode is in the ignition state. And the switching element for the main electrode is in the ignition state based on the information from the ignition state determination circuit 46 for the main electrode and the ignition state determination circuit 48 for the bottom electrode. While the switching element is extinguished Only between the instantaneous value of the voltage between the bottom electrode 6 and one of the main electrodes 5 and the instantaneous value of the current between the bottom electrode 6 and one of the main electrodes 5, the power between the bottom electrode and one of the main electrodes 5. Of the power between the main electrodes 5 based on a value obtained by subtracting the instantaneous value of the power between the bottom electrode 6 and one of the main electrodes 5 from the instantaneous value of the power between the main electrodes 5. Configure to find and output the value,
Multiplier 39 ′ that multiplies the instantaneous voltage value v ₁ between the main electrodes 5 and the instantaneous current value i ₁ to output the instantaneous power value, the bottom electrode ignition state determination circuit 48, and the main electrode ignition state Based on the information from the determination circuit 46, the main electrode 5 output from the multiplier 39 'is switched to the c side only while the bottom electrode switching element is in the ignition state and the main electrode switching element is in the arc extinction state. Based on the instantaneous value of the power between the bottom electrode 6 and one of the main electrodes 5 output from the multiplier 43 through the switch 61, the multiplier 60 'that outputs the instantaneous value of the voltage between the multiplier 43' And a subtractor 63 that outputs to the integrator 44 a value obtained by subtracting the instantaneous value of the power between the main electrodes 5 output from 39 'through the switch 60'. In the value calculation circuit 42, the bottom electrode ignition state determination Based on the information from the circuit 48, the instantaneous value of the voltage between the bottom electrode 6 and one of the main electrodes 5 and between the bottom electrode and one of the main electrodes 5 only while the switching element for the bottom electrode is in an ignition state. The instantaneous value of the electric power between the bottom electrode 6 and one of the main electrodes 5 is obtained from the instantaneous value of the current, and information from the main electrode ignition state determination circuit 46 and the bottom electrode ignition state determination circuit 48 is used as information. On the basis of the instantaneous value of the voltage between the main electrodes 5 and the instantaneous value of the current between the main electrodes 5 only when the bottom electrode switching element is in the ignition state and the main electrode switching element is in the arc extinguishing state, And the bottom electrode 6 and the main electrode based on a value obtained by subtracting the instantaneous value of the power between the main electrodes 5 from the instantaneous value of the power between the bottom electrode 6 and one of the main electrodes 5. Obtain and output the effective value of power between one of 5 It is in the point constituted as follows.

  Based on information from the main electrode ignition state determination circuit 46 and the bottom electrode ignition state determination circuit 48, the switch 61 ′ indicates that the main electrode switching element is in the extinguishing state or the bottom electrode switching element is While it is in the ignition state, it is switched to the d side and outputs 0 (zero), and the switch 60 'includes the bottom electrode ignition state determination circuit 48 and the main electrode ignition state determination circuit. Based on the information from 46, while the bottom electrode switching element is in the arc extinguishing state or the main electrode switching element is in the ignition state, it is switched to the d side and outputs 0 (zero).

  When a self-excited element such as IGBT is used as the main electrode switching element and the bottom electrode switching element, the main electrode ignition state determination circuit 46 and the bottom electrode ignition state determination circuit 48 are respectively As in the case of the main electrode voltage effective value calculation circuit 18 and the bottom electrode voltage effective value calculation circuit 23, the configuration shown in FIG.

  When separately excited elements such as thyristors are used as the main electrode switching element and the bottom electrode switching element, the main electrode ignition state determination circuit 46 and the bottom electrode ignition state determination circuit 48 are respectively As in the case of the electrode voltage effective value calculation circuit 18 and the bottom electrode voltage effective value calculation circuit 23, the configuration shown in any of FIGS. 3, 4, 5, and 6 can be employed.

  Next, the operation of the example shown in FIG. 10 will be described.

  In the main electrode power effective value calculation circuit 38, the switch 60 is switched to the a side only while the main electrode switching element is in the ignition state based on the information from the main electrode ignition state determination circuit 46, and multiplication is performed. The instantaneous value of the power between the main electrodes 5 from the device 39 is output to the subtractor 62, and based on the information from the main electrode ignition state determination circuit 46 and the bottom electrode ignition state determination circuit 48, The switch 61 'is switched to the c side only while the switching element is in an ignition state and the bottom electrode switching element is in an arc extinction state, and the bottom electrode 6 from the multiplier 43' and one of the main electrodes 5 are switched. Between the bottom electrode 6 and one of the main electrodes 5 is subtracted from the instantaneous power value between the main electrodes 5 in the subtractor 62. The value obtained by the integrator 4 Since the effective value of power between the main electrodes 5 is obtained and outputted, the net effective power value can be obtained more accurately.

  In the bottom electrode power effective value calculation circuit 42, the switch 61 is switched to the a side only while the bottom electrode switching element is in the ignition state based on the information from the bottom electrode ignition state determination circuit 48. The instantaneous value of the electric power between the bottom electrode 6 and one of the main electrodes 5 from the device 43 is output to the subtractor 63, and the main electrode ignition state determination circuit 46 and the bottom electrode ignition state determination circuit Based on the information from 48, the switch 60 'is switched to the c side only while the bottom electrode switching element is in the ignition state and the main electrode switching element is in the arc extinction state, and the main electrode from the multiplier 39' 5 is output to the subtracter 63, and the subtracter 63 calculates the instantaneous power value between the main electrodes 5 from the instantaneous power value between the bottom electrode 6 and one of the main electrodes 5. The subtracted value is obtained Since this is output to the integrator 44 and the effective value of the power between the bottom electrode 6 and the main electrode 5 is obtained and output, the net effective power value can be obtained more accurately.

Here, the net electric power charged in the electric melting furnace excluding the loss consumed outside the electric melting furnace is given by the following expression by subtracting the electric power consumed outside the furnace from the equation [15].

  Note that the arc extinguishing timing may be delayed from the ideal timing T due to the inductance of the circuit, and may shift to the next cycle. Even in such a case, the present circuit can calculate the net effective power value.

  As a result, the controllability of the operation of the electric melting furnace is improved, the degree of freedom of arrangement of the main electrode switching element and the bottom electrode switching element in the electric circuit is increased, and the object to be melted such as glass having a very low current resistance. On the other hand, in an electric melting furnace that requires energization control with a low voltage and a large current, expensive switching elements such as thyristors 10 and 13 are arranged on the high voltage and small current side of the transformers 8 and 11 (see FIG. 13). The rated current capacity can be set and designed lower than when a switching element is installed on the low voltage / large current side (see FIG. 14), which has the merit of leading to a significant cost reduction of the device. On the contrary, it is possible to select the installation of the transformers 8 and 11 on the low voltage side as necessary from the viewpoint of the withstand voltage of the switching element, and it is possible to flexibly respond to individual requests that differ from plant to plant.

  In this way, the effective power value can be grasped more accurately, the controllability of the operation can be improved, the degree of freedom of the arrangement of the switching elements in the electric circuit is increased, and the individual requirements that differ from plant to plant as well as cost reduction. Can respond flexibly.

  FIG. 11 is a schematic configuration diagram showing a first example of a power supply control panel in an example of an embodiment of the present invention. In the figure, parts denoted by the same reference numerals as those in FIG. The general configuration is the same as that of the conventional one shown in FIG. 22, but the characteristic feature of this illustrated example is that the voltage and current between the main electrodes 5 or the main electrode 5 itself are changed as shown in FIG. In addition to the detection from the latest, the voltage and current between the bottom electrode 6 and one of the main electrodes 5 are detected from the bottom electrode 6 itself or from the immediate vicinity of the bottom electrode 6.

  In electric melting furnaces that handle low resistance materials such as glass, there is a tendency for low voltage and large current, voltage drop due to cable resistance and contact resistance such as power cables and bus bars laid from the power supply control panel to the electric melting furnace, Although the power loss is a non-negligible amount, as described above, the voltage and current between the main electrodes 5 are detected from the main electrode 5 itself or from the vicinity of the main electrode 5 and between the bottom electrode 6 and one of the main electrodes 5. By configuring the voltage and current to be detected from the bottom electrode 6 itself or from the immediate vicinity of the bottom electrode 6, it is possible to exclude the voltage drop and power loss due to the cable, and the calculation of the effective values of voltage, current, and power becomes more meaningful. It becomes possible to carry out.

  In addition, when the stray capacitance component on the circuit is sufficiently small and can be ignored, the current flowing on the circuit is unique regardless of the measurement location. Therefore, the first example of the power supply control panel in the embodiment of the present invention shown in FIG. As in the two examples, only the voltage between the main electrodes 5 is detected from the main electrode 5 itself, and only the voltage between the bottom electrode 6 and one of the main electrodes 5 is detected from the bottom electrode 6 itself. Even in this case, an improvement effect can be sufficiently obtained when the effective values of voltage, current, and power are calculated more meaningfully.

  Note that the electric melting furnace of the present invention is not limited to the above-described illustrated examples, and the switching element for the main electrode and the switching element for the bottom electrode are not limited to thyristors and IGBTs, and other switching elements are also available. It goes without saying that various changes can be made without departing from the scope of the present invention, such as being employable.

It is a block diagram which shows the voltage effective value calculation circuit for main electrodes and the voltage effective value calculation circuit for bottom electrodes in an example of embodiment which implements this invention. It is a block diagram which shows the 1st example of the ignition state determination circuit for main electrodes and the ignition state determination circuit for bottom electrodes in an example of embodiment which implements this invention. It is a block diagram which shows the 2nd example of the ignition state determination circuit for main electrodes and the ignition state determination circuit for bottom electrodes in an example which implements this invention. It is a block diagram which shows the 3rd example of the ignition state determination circuit for main electrodes and the ignition state determination circuit for bottom electrodes in an example which implements this invention. It is a block diagram which shows the 4th example of the ignition state determination circuit for main electrodes and the ignition state determination circuit for bottom electrodes in an example of embodiment which implements this invention. It is a block diagram which shows the 5th example of the ignition state determination circuit for main electrodes and the ignition state determination circuit for bottom electrodes in an example which implements this invention. It is a diagram which shows the voltage effective value in an example of embodiment which implements this invention. It is a block diagram which shows the current effective value calculation circuit for main electrodes and the current effective value calculation circuit for bottom electrodes in an example of embodiment which implements this invention. It is a block diagram which shows the power effective value calculation circuit for main electrodes and the power effective value calculation circuit for bottom electrodes in an example which implements this invention. It is a block diagram which shows the modification of the electric power effective value calculation circuit for main electrodes and the electric power effective value calculation circuit for bottom electrodes in an example of embodiment which implements this invention. It is a schematic block diagram which shows the 1st example of the electric power feeding control panel in an example of embodiment which implements this invention. It is a schematic block diagram which shows the 2nd example of the electric power feeding control board in an example of embodiment which implements this invention. It is the schematic which shows an example of the conventional electric melting furnace. It is the schematic which shows the other example of the conventional electric melting furnace. (A) is a diagram which shows the energization voltage waveform to the switching element for main electrodes and the switching element for bottom electrodes, (b) is a figure which shows the equivalent in-furnace model of an electric melting furnace. It is a diagram which shows a measurement voltage waveform (when β <α). It is a block diagram which shows the conventional voltage effective value calculation circuit for main electrodes, and the voltage effective value calculation circuit for bottom electrodes. It is a diagram which shows a measurement current and a voltage waveform (when β <α). It is a block diagram which shows the conventional current effective value calculation circuit for main electrodes and the current effective value calculation circuit for bottom electrodes. It is a diagram which shows measured electric power and a voltage waveform (when β <α). It is a block diagram which shows the conventional power effective value calculation circuit for main electrodes and the power effective value calculation circuit for bottom electrodes. It is a schematic block diagram which shows an example of the conventional electric power feeding control panel.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Melting space 3 Melting furnace main body 4 Input port 5 Main electrode 6 Bottom electrode 7 Downflow port 8 Main electrode transformer 9 Main electrode power source 10 Thyristor (main electrode switching element)
11 Transformer for bottom electrode 12 Power supply for bottom electrode 13 Thyristor (switching element for bottom electrode)
14 Main Electrode Voltmeter 15 Main Electrode Ammeter 16 Bottom Electrode Voltmeter 17 Bottom Electrode Ammeter 18 Main Electrode Voltage RMS Calculation Circuit 23 Bottom Electrode Voltage RMS Calculation Circuit 28 Main Electrode Current RMS Calculation Circuit 33 RMS current calculation circuit for bottom electrode 38 RMS power calculation circuit for main electrode 42 RMS power calculation circuit for bottom electrode 46 ignition condition determination circuit for main electrode 47 switch 48 ignition condition determination circuit for bottom electrode 49 Switcher 50 Gate control circuit 51 Gate signal 52 Start circuit 53 Start signal 54 Voltage difference determination circuit 55 Single flip-flop 56 Current value determination circuit 57 Single flip-flop 58 Switcher 59 Switcher 60 Switcher 60 'Switcher 61 Switch 61 'Changer 62 Subtractor 63 Subtractor

Claims (10)

A pair of a melting furnace body in which a flow-down port is formed at the bottom, and a pair of the melting furnace body that is disposed opposite to an intermediate portion in the vertical direction of the inner wall of the melting furnace body and that heats and melts the melt in the melting furnace body by energization between them. An electric current is passed between the main electrode and the bottom electrode which is disposed at the bottom of the melting furnace body and heats and melts the material to be melted inside the melting furnace body by energization between the main electrode and one of the main electrodes. A main electrode power source having a main electrode transformer for the main electrode, a main electrode switching element provided on either the primary coil side or the secondary coil side of the main electrode transformer of the main electrode power source, A bottom electrode power source having a bottom electrode transformer for energizing between the bottom electrode and one of the main electrodes, and either the primary coil side or the secondary coil side of the bottom electrode transformer of the bottom electrode power source Bottom power provided on In electric melting furnace comprising a use switching elements,
A main electrode ignition state determination circuit for determining whether the main electrode switching element is in an ignition state or an extinguishing state;
Based on information from the main electrode ignition state determination circuit, the main electrode voltage is obtained by obtaining the effective value of the voltage from the instantaneous value of the voltage between the main electrodes and outputting it only while the main electrode switching element is in the ignition state. An effective value calculation circuit;
A bottom electrode ignition state determination circuit for determining whether the bottom electrode switching element is in an ignition state or an extinguishing state; and
Based on the information from the bottom electrode ignition state determination circuit, the effective value of the voltage is obtained from the instantaneous value of the voltage between the bottom electrode and one of the main electrodes only while the bottom electrode switching element is in the ignition state. An electric melting furnace comprising: a voltage effective value calculation circuit for a bottom electrode that outputs power at a bottom. A pair of a melting furnace body in which a flow-down port is formed at the bottom, and a pair of the melting furnace body that is disposed opposite to an intermediate portion in the vertical direction of the inner wall of the melting furnace body and that heats and melts the melt in the melting furnace body by energization between them. An electric current is passed between the main electrode and the bottom electrode which is disposed at the bottom of the melting furnace body and heats and melts the material to be melted inside the melting furnace body by energization between the main electrode and one of the main electrodes. A main electrode power source having a main electrode transformer for the main electrode, a main electrode switching element provided on either the primary coil side or the secondary coil side of the main electrode transformer of the main electrode power source, A bottom electrode power source having a bottom electrode transformer for energizing between the bottom electrode and one of the main electrodes, and either the primary coil side or the secondary coil side of the bottom electrode transformer of the bottom electrode power source Bottom power provided on In electric melting furnace comprising a use switching elements,
A main electrode ignition state determination circuit for determining whether the main electrode switching element is in an ignition state or an extinguishing state;
Based on the information from the main electrode ignition state determination circuit, the main electrode current is obtained by obtaining the effective value of the current from the instantaneous value of the current between the main electrodes and outputting it only while the main electrode switching element is in the ignition state. An effective value calculation circuit;
A bottom electrode ignition state determination circuit for determining whether the bottom electrode switching element is in an ignition state or an extinguishing state; and
Based on the information from the bottom electrode ignition state determination circuit, the effective value of the current is obtained from the instantaneous value of the current between the bottom electrode and one of the main electrodes only while the bottom electrode switching element is in the ignition state. And an electric current effective value calculation circuit for the bottom electrode that outputs the electric current. A pair of a melting furnace body in which a flow-down port is formed at the bottom, and a pair of the melting furnace body that is disposed opposite to an intermediate portion in the vertical direction of the inner wall of the melting furnace body and that heats and melts the melt in the melting furnace body by energization between them. An electric current is passed between the main electrode and the bottom electrode which is disposed at the bottom of the melting furnace body and heats and melts the material to be melted inside the melting furnace body by energization between the main electrode and one of the main electrodes. A main electrode power source having a main electrode transformer for the main electrode, a main electrode switching element provided on either the primary coil side or the secondary coil side of the main electrode transformer of the main electrode power source, A bottom electrode power source having a bottom electrode transformer for energizing between the bottom electrode and one of the main electrodes, and either the primary coil side or the secondary coil side of the bottom electrode transformer of the bottom electrode power source Bottom power provided on In electric melting furnace comprising a use switching elements,
A main electrode ignition state determination circuit for determining whether the main electrode switching element is in an ignition state or an extinguishing state;
Based on the information from the main electrode ignition state determination circuit, the power between the main electrodes is determined from the instantaneous value of the voltage between the main electrodes and the instantaneous value of the current between the main electrodes only while the switching element for the main electrode is in the ignition state. Power effective value calculation circuit for the main electrode that calculates and outputs the effective value of
A bottom electrode ignition state determination circuit for determining whether the bottom electrode switching element is in an ignition state or an extinguishing state; and
Based on the information from the bottom electrode firing state determination circuit, the instantaneous value of the voltage between the bottom electrode and one of the main electrodes and one of the bottom electrode and the main electrode only while the bottom electrode switching element is in the firing state. An electric melting furnace comprising: a bottom electrode power rms value calculation circuit that obtains and outputs an effective value of power between the bottom electrode and one of the main electrodes from an instantaneous current value between the bottom electrode and the main electrode. A pair of a melting furnace body in which a flow-down port is formed at the bottom, and a pair of the melting furnace body that is disposed opposite to an intermediate portion in the vertical direction of the inner wall of the melting furnace body and that heats and melts the melt in the melting furnace body by energization between them. An electric current is passed between the main electrode and the bottom electrode which is disposed at the bottom of the melting furnace body and heats and melts the material to be melted inside the melting furnace body by energization between the main electrode and one of the main electrodes. A main electrode power source having a main electrode transformer for the main electrode, a main electrode switching element provided on either the primary coil side or the secondary coil side of the main electrode transformer of the main electrode power source, A bottom electrode power source having a bottom electrode transformer for energizing between the bottom electrode and one of the main electrodes, and either the primary coil side or the secondary coil side of the bottom electrode transformer of the bottom electrode power source Bottom power provided on In electric melting furnace comprising a use switching elements,
A main electrode ignition state determination circuit for determining whether the main electrode switching element is in an ignition state or an extinguishing state;
A bottom electrode ignition state determination circuit for determining whether the bottom electrode switching element is in an ignition state or an extinguishing state; and
Based on the information from the main electrode ignition state determination circuit, the power between the main electrodes is determined from the instantaneous value of the voltage between the main electrodes and the instantaneous value of the current between the main electrodes only while the switching element for the main electrode is in the ignition state. And the main electrode switching element is in an ignition state and the bottom electrode switching element is extinguished based on information from the main electrode ignition state determination circuit and the bottom electrode ignition state determination circuit. The power of the power between the bottom electrode and one of the main electrodes is determined from the instantaneous value of the voltage between the bottom electrode and one of the main electrodes and the instantaneous value of the current between the bottom electrode and one of the main electrodes only while in the state. An instantaneous value is obtained, and an effective value of the power between the main electrodes is obtained and output based on a value obtained by subtracting the instantaneous value of the power between the bottom electrode and one of the main electrodes from the instantaneous value of the power between the main electrodes. A power effective value calculation circuit for the main electrode,
Based on the information from the bottom electrode ignition state determination circuit, the instantaneous value of the voltage between the bottom electrode and one of the main electrodes and one of the bottom electrode and the main electrode only while the bottom electrode switching element is in the ignition state. The instantaneous value of the electric power between the bottom electrode and one of the main electrodes is obtained from the instantaneous value of the current between the main electrode and the information from the main electrode ignition state determination circuit and the bottom electrode ignition state determination circuit. Based on the instantaneous value of the voltage between the main electrodes and the instantaneous value of the current between the main electrodes, only when the bottom electrode switching element is in the ignition state and the main electrode switching element is in the arc extinguishing state, An instantaneous value is obtained, and the electric power between the bottom electrode and one of the main electrodes is obtained by subtracting the instantaneous value of the electric power between the main electrodes from the instantaneous value of the electric power between the bottom electrode and the main electrode. For the bottom electrode that calculates and outputs the effective value of Electric melting furnace, characterized in that a effective value calculating circuit. Each of the main electrode switching element and the bottom electrode switching element is a self-excited element capable of arbitrarily controlling the ON / OFF timing,
Each of the main electrode ignition state determination circuit and the bottom electrode ignition state determination circuit is configured to determine the ignition state of the self-excited element based on a gate signal output from the gate control circuit of the self-excited element. The electric melting furnace as described in any one of Claims 1-4. Each of the main electrode switching element and the bottom electrode switching element is a separately excited element that can arbitrarily control the ON timing but cannot control the OFF timing.
The main electrode ignition state determination circuit and the bottom electrode ignition state determination circuit each determine a voltage difference before and after a separately excited element that is in an ignition state by an ignition signal output from the ignition circuit. When the voltage difference is V _L or less and it is determined that the separately excited element is in an ignition state, and the voltage difference is V _H or more and the forward voltage drop is large, the separately excited element is in an arc extinguished state. The electric melting furnace as described in any one of Claims 1-4 comprised so that it might determine. Each of the main electrode switching element and the bottom electrode switching element is a separately excited element that can arbitrarily control the ON timing but cannot control the OFF timing.
The main electrode firing state determination circuit and the bottom electrode firing state determination circuit each set a single flip-flop by the firing signal output from the firing circuit of the separately excited element, and the separately excited element is in the firing state. The voltage difference before and after the separately excited element that is in the ignition state is detected by the voltage difference determination circuit based on the ignition signal output from the ignition circuit, and the forward voltage is detected when the voltage difference is V _H or more. The electric melting furnace as described in any one of Claims 1-4 comprised so that it might be determined that the single flip-flop is reset and the separately excited element is in an arc extinguishing state when the descent is large. Each of the main electrode switching element and the bottom electrode switching element is a separately excited element that can arbitrarily control the ON timing but cannot control the OFF timing.
The main electrode ignition state determination circuit and the bottom electrode ignition state determination circuit each detect a holding current of a separately excited element that is in an ignition state based on an ignition signal output from the ignition circuit, by a current value determination circuit. Wherein the holding current is not more than I _L and it is determined that the separately excited element is in an ignition state, and the holding current is not less than I _H and it is determined that the separately excited element is in an arc extinguishing state. 4. The electric melting furnace according to any one of 4 above. Each of the main electrode switching element and the bottom electrode switching element is a separately excited element that can arbitrarily control the ON timing but cannot control the OFF timing.
The main electrode firing state determination circuit and the bottom electrode firing state determination circuit each set a single flip-flop by the firing signal output from the firing circuit of the separately excited element, and the separately excited element is in the firing state. It determines that the said single flip-flop at said point by firing signal outputted from the firing circuit detects the holding current of the separately excited element to be firing state by the current value determination circuit, the holding current I _H or The electric melting furnace as described in any one of Claims 1-4 comprised so that it might determine that a separately excited type element is in an arc extinguishing state by resetting.   At least the voltage and current between the main electrodes are detected from the main electrode itself or from the vicinity of the main electrode, and at least the voltage and current between the bottom electrode and one of the main electrodes is detected from the bottom electrode itself or the vicinity of the bottom electrode. The electric melting furnace as described in any one of Claims 1-9 comprised so that it might detect from.

Images