JP2008027735A - Power-supply unit for induction heating device, induction heating device, and hot metal holding furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid high-voltage overcurrent trip, even with respect to temporary sudden change in the inductance of the system as a whole, including an induction heating device and a heating object by expanding the variable range of capacitor capacitance, using a simple and low-cost constitution. <P>SOLUTION: In this power-supply unit 100 of an induction heating device, equipped with a capacitance-fixed capacitor group 130F and a capacitance-variable capacitor group 130V, a part of the capacitance-fixed capacitor group 130F can be separated collectively from a circuit by a manual switch (for instance, a high-voltage disconnector 142). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an induction heating apparatus power supply apparatus, induction heating apparatus, and hot metal holding furnace, and more particularly to an induction heating apparatus power supply apparatus including a fixed capacity capacitor group and a variable capacity capacitor group, and an induction heating apparatus including the power supply apparatus. The present invention also relates to a hot metal holding furnace provided with this induction heating device.

  FIG. 5 is a circuit diagram showing a power supply device 100 of a conventional induction heating device. In a large-scale (2000 kVA or more) induction heating apparatus power supply apparatus that is operated by a commercial power supply, for example, it receives power from a three-phase AC commercial power supply via the high-voltage circuit breaker 110 and passes through the three-phase balanced circuit 120 to become a single phase. After the adjustment, electric power is supplied to the induction heating device 200 composed of a single-phase load, but the single-phase load in this case needs to be operated so that the power factor becomes 1.

  Since the induction heating device 200 is a so-called delayed load in which the phase of the alternating current flowing with respect to the supplied alternating voltage is delayed, the capacitor 130 is usually connected in parallel with the induction heating device 200 in order to improve the power factor. Connect at least the capacity equivalent to the capacitance of the entire system including the induction heating device and the object to be heated (1.5 to 2 times that of the induction heating device).

  Capacitor 130 is generally configured to have a variable capacity to some extent according to circuit resistance (inductance of induction heating apparatus 200 and the entire system including an object to be heated) that may change over time. .

  FIG. 6 schematically shows a capacitor panel 132 in which such a capacitor 130 is accommodated. The capacitor 130 has two terminals of each capacitor 134 connected to the two bus bars 136 constituting the R phase and the T phase, respectively. 5 corresponds to the variable portion 130V in FIG. 5 described above, and the two terminals of each capacitor 134 are connected / disconnected with the two bus bars 136 constituting the R phase and the T phase, respectively. By increasing the number of capacitors 134 connected to the bus bar 136, the capacitor capacity (capacitance) of the power supply apparatus 100 as a whole is increased in stages, and conversely, the capacitor 134 separated from the bus bar 136. By increasing the number of power supplies, the capacitance of the power supply device 100 as a whole can be reduced step by step. It has become.

As described above, the capacitance of the power supply device 100 as a whole is normally configured to be changed in stages. However, the capacitance of the power supply device 100 as a whole is represented by C (F), induction heating. When the inductance of the entire system including the apparatus 200 and the object to be heated is L (H), the induction heating apparatus 200 is
Resonance frequency f = (2π) ⁻¹ (LC) ^−1/2
As a result, it oscillates.

  Here, as shown in FIG. 7, the induction heating device includes an induction heating device main body 200 composed of a copper coil, a cable 300, and a capacitor panel 132, while excluding the object to be heated 400. The power supply device 100 is included and configured as an induction heating device as a whole.

  Patent Document 1 and Patent Document 2 include an example in which power is received from a three-phase AC commercial power supply, adjusted to a single phase via a three-phase balanced circuit, and then supplied to an induction heating device composed of a single-phase load. Are listed.

  In addition, although the induction heating apparatus is often used in the fields of metal refining, processing, welding and the like as in Patent Document 3, Patent Document 4, and Patent Document 5, of course, the present invention is applicable to those fields. It is not limited to things.

Japanese Patent Laid-Open No. 61-042992 JP 59-224092 A JP 2004-218038 A Japanese Patent No. 3781456 Japanese Patent No. 3492408

  In the induction heating apparatus such as Patent Document 1 and Patent Document 2, as shown in FIGS. 5 and 6, all the capacitors 134 can be individually connected and disconnected via the switch 138, that is, configured as a variable capacity component. However, in the power supply apparatus 100 of the induction heating apparatus, the capacitor is usually divided into a fixed part 130F and a variable part 130V.

  The reason is that if all the capacitors are provided with a mechanism that can be connected / disconnected, all of them require a disconnecting device (switch 138) from the circuit, resulting in a very expensive device.

  Therefore, normally, about 1/4 of the total capacitor capacity is made variable, and variable switching is made about 10 steps. For example, when there is an induction heating device 200 of 1000 kW (2000 kVA), the power factor improving capacitor 130 requires 3600 kVA, of which 2600 kVA is a fixed capacitor 130F and 1000 kVA is a variable capacity capacitor 130V. The capacitor 130V having a variable capacity of 1000 kVA can be connected to and disconnected from the circuit by a high-pressure vacuum switch 138 every 100 kVA, for example.

  The power supply apparatus 100 for the induction heating apparatus is designed to be fine as long as the change in inductance of the entire system including the induction heating apparatus main body 200 and the object to be heated 400 is up to 25% (1/4). become. Empirically, in the induction heating apparatus, when the inductance of the entire system including the induction heating apparatus main body 200 and the object to be heated 400 changes by 20% or more, it is recommended to replace the induction heating apparatus main body 200 itself. Therefore, 25% of the variable amount of the capacitor is sufficient.

  However, depending on the application, the inductance of the entire system including the induction heating apparatus main body 200 and the object to be heated 400 often does not change stably, and the change in inductance may reach 30% or more. In this case, in the power supply apparatus 100 of the induction heating apparatus as described above, an overcurrent is generated in the circuit, resulting in a high voltage overcurrent trip.

  When this state occurs, in the case of the power supply device 100 of the conventional induction heating device as described above, the induction heating device main body 200 itself needs to be replaced quickly, but it is reasonable from the viewpoint of achieving the device life. is not.

  The present invention has been made to solve the above-described conventional problems, and by using a simple and inexpensive configuration, the variable range of the capacitor capacity is expanded, and the inductance of the entire system including the induction heating device and the object to be heated is temporarily increased. It is an object to make it possible to avoid a high-voltage overcurrent trip even for a sudden sudden change.

  In the present invention, in order to solve the above-described problem, a part of the capacitors conventionally treated as fixed parts, for example, half of the capacitors, can be easily separated in a lump. That is, the present invention is as follows.

(1) In an induction heating apparatus power supply device including a fixed-capacitance capacitor group and a variable-capacitance capacitor group, a part of the fixed-capacitance capacitor group can be collectively separated from the circuit. Power supply for heating device.

(2) An induction heating device comprising the power supply device of (1).

(3) A hot metal holding furnace comprising the induction heating device of (2).

  According to the present invention, since a part of the capacitors conventionally treated as fixed parts, for example, half of the capacitors can be easily separated at a time, the circuit resistance is 10 to 20% after the middle of the device life. When it has changed to some extent (with all of the variable capacitors disconnected), a part of the fixed capacitors, for example, half of them are disconnected, so that the variable range of the capacitor capacity (the capacitor is disconnected and the capacitance is reduced. The variable range of direction) can be increased, and the capacitor can be switched even when the inductance of the entire system including the induction heating apparatus main body 200 and the object to be heated 400 is suddenly changed. Can be avoided.

  In general, the inductance change of the entire system including the induction heating apparatus main body 200 and the object to be heated 400 is about 20%, which is the limit of use of the induction heating apparatus main body 200 itself. Even if the inductance of the entire system including the induction heating apparatus main body 200 and the object 400 to be heated changes by 40% or more, it can be used and the life can be extended.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  In this embodiment, in the power supply apparatus 100 similar to that shown in FIG. 5, as shown in FIG. 1, of a part of the capacitor 130 for improving the power factor, that is, out of the fixed portion 130F (for example, 75%) Half (for example, 37%) can be easily separated at once by a high-pressure discon 142 which is an inexpensive and easy manual separation device.

  As a result, the variable range of the capacitor capacity can be increased from the conventional 25% to 60% or more, and a temporary sudden change in the inductance of the entire system including the induction heating apparatus main body 200 and the object to be heated 400 can be achieved. Capacitor switching becomes possible and high voltage overcurrent trips can be avoided.

  In general, the inductance change of the entire system including the induction heating apparatus main body and the object to be heated is about 20%, which is the limit of use of the induction heating apparatus main body itself. Even if the inductance of the entire system including the heating device main body and the object to be heated changes by 40% or more, it can be used and the life can be extended.

  The embodiment of the present invention shown in FIG. 1 is an example in which the induction heating device 200 is 2000 kVA and the power factor correction capacitor 130 is 3600 kVA.

  Of the 3600 kVA, the variable capacitor group 130V is for 1000 kVA, and the fixed capacitor group 130F is 2600 kVA. By applying the present invention, the 1300 kVA portion of the fixed capacitor group 130F can be collectively disconnected from the circuit by a knife switch-like mechanism 142 that can be connected / disconnected as shown in FIG. It has a configuration. Note that the symbols R and C shown in the front view of FIG. 2A are connected to the R-phase and capacitor 134 in FIG.

  The high-voltage discon 142 is housed in the storage board 140, but as shown in FIG. 3, the high-voltage discon storage board 140 is installed outside the capacitor board 132 as a whole. The terminals connected to the R phase of several capacitors 134 connected to the R phase in the conventional capacitor panel 132 shown in FIG. 6 are collectively connected to one side of the high voltage discon 142 via the cable 144. Is connected to the terminal. Then, the other terminal of the high-voltage discon 142 is also connected to the R phase via the cable 144. The other terminal of the capacitor 134 is connected to the T-phase side, which is the same as the conventional capacitor panel 132 shown in FIG.

  The above-described example is for an induction heating apparatus used in a hot metal holding furnace 500 as shown in FIG. 4 (A). As shown in detail in FIG. 4 (B), a stamp (powder) refractory is used. Is coated around a core material that becomes a passage for molten metal (also referred to as molten metal), and the induction heating device main body 200 is formed in a block 510 formed by melting the core material to form a tunnel, and an induction consisting of an O-shaped iron core and a coil. A heater (also referred to as an inductor) 210 is created by inserting it into a separately hollowed hole. In FIG. 4 (A), 520 is a hot metal inlet, 530 is a scrap inlet, and 540 is a tap.

  In such an example, when operated for several months, the slag adheres and accumulates on the inner wall of the block 510 formed in a tunnel shape, and as a result, the inductance of the entire system including the induction heating device 200 and the object to be heated may change greatly. However, as shown in this example, when several months have passed, if a group of capacitors that can be separated from the circuit by manipulating the high-voltage discon 142 by manpower operation is collectively separated from the circuit, The voltage overcurrent trip can be avoided.

  In a state where the inductance of the entire system including the induction heating apparatus and the object to be heated is changed by about 20% (after the middle of the life), the variable capacitor group 130V is separated by about 800 kVA, and as a whole 2800 kVA. A capacitor is connected.

  If a factor that causes the inductance of the entire system including the induction heating device and the object to be heated to fluctuate by about 40% even in this state, the entire circuit of the entire system including the induction heating device and the object to be heated is Leading power factor and high voltage overcurrent trip occurs.

  Therefore, when 1300 kVA of the fixed capacitance capacitor group 130F is changed to a capacitor group configured such that a plurality of capacitors can be separated from the circuit in a lump, and combined with the variable capacitance capacitor group 130V, the entire variable amount is set to 2300 kVA At that moment, there is a slight delay power factor, but even if the inductance of the entire system including the induction heating device and the object to be heated fluctuates by 40%, a high voltage overcurrent trip will not occur.

  Compared to the case where the investment of the type that uses 1300kVA in several steps with the conventional variable capacitor method is used, the construction cost is 60% when the collective manual disconnection method of the present invention is adopted. Could be implemented.

  With regard to the life, in the conventional method, when the operation is performed for about 4 months, high voltage overcurrent trips frequently occur, and the remaining life as a refractory has to be replaced. It became usable until a month.

  In the case of this example, as shown in FIG. 3, the high-voltage discon 142 is provided in a high-voltage discon storage board 140 that is different from the capacitor board 132 and is placed separately from the capacitor board 132. There is no need to place anything separately in this way, and the high voltage discon 142 may be provided in the capacitor panel 132.

  The type of switch for performing manual disconnection collectively is not limited to the high pressure discon 142, and the application target is not limited to the hot metal holding furnace.

The circuit diagram which shows the power supply device of one Embodiment of this invention The (A) front view and (B) side view which show the high voltage | pressure discon storage board of the said embodiment. The perspective view which shows the capacitor | condenser board of the said embodiment The (A) whole figure and (B) detailed drawing which show the hot metal holding furnace which is an example of the application object of this invention Circuit diagram showing a conventional power supply device A perspective view showing an example of a conventional capacitor panel Diagram showing the overall configuration of the induction heating device

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Power supply device 130 ... Capacitor 130F ... Capacitance fixed capacitor 130V ... Capacitance variable capacitor 132 ... Capacitor panel 136 ... Busbar 138 ... Switch 140 ... High voltage discon storage panel 142 ... High voltage discon 144, 300 ... Cable 200 ... Induction heating apparatus main body 400 ... Object to be heated

Claims (3)

In the power supply device of the induction heating device provided with a fixed capacitance capacitor group and a variable capacitance capacitor group,
A power supply device for an induction heating device, wherein a part of the fixed-capacitance capacitor group can be collectively separated from a circuit.   An induction heating apparatus comprising the power supply device according to claim 1.   A hot metal holding furnace comprising the induction heating device according to claim 2.

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