SU1492489A1 - Device for control of electric mode of three-phase arc steelmaking electric furnace - Google Patents

Abstract

The invention relates to electrical engineering. The purpose of the invention is to increase productivity and reduce specific energy consumption by reducing the time of charge melting. During the smelting process, an automatic selection of the optimum melting current is provided and its increase to the nominal value as the arc conditions improve. 2 Il.

Description

(21) 4183952 / 24-07

(22) 01/21/87

(46) 07.07.89. Bul Number 25

(71) A special design bureau of the Scientific-Production

 Chermetavtomatika Association

(72) V.N. Kuznetsov, A.P. Petrov, V.L. Savchenko, Yu.P. Zorikov

and V.A. Novikov (53) 621.365.22 (088.8) (56) U.S. Patent No. 3914526, cl. 13-13, 1975.

Author's certificate of the USSR No. 1247640, cl. H 05 B 7/148, 1986.

(54) A DEVICE FOR CONTROLLING A ELECTRICAL TREATMENT MODE OF A THREE-PHASE ARC STEEL-MELTING ELECTRIC TERMINAL (57) The invention relates to electrical engineering. Pel of the invention is to increase the productivity and reduce the specific energy consumption by reducing the melting time of the imht. During the smelting process, an automatic selection of the optimum melting current is provided and its increase to the nominal value as the arc conditions improve. 2 Il.

Testing is related to electrothermia, in particular to smelting steel and ferroalloys in arc furnaces, and can be used in electrometallurgy to regulate the power of an arc furnace by moving electrodes.

The aim of the invention is to increase the productivity of the arc furnace and reduce the specific energy consumption by reducing the melting time of the charge.

Fig. 1 is a block diagram of a device for controlling the electrical mode of a three-phase electric arc furnace; in fig. 2 is a block diagram of a correction device.

The device (Fig. 1) contains, in the control circuit of each phase, an arc current sensor 1, an arc voltage sensor 2, a threshold setting unit 3, an electric mode analyzer 4, a correction

5, two keys 6 and 7, a power controller 8, a thyristor block 9, an execution mechanism using a DC motor 10, equipped with a core current sensor 11 and a rotation speed sensor 12, common for all phases driver 13 of the prohibitions, the dead zone setting unit 14 and the arc current setting unit 15, the output of the arc current sensor 1 of each phase is connected to the first input of the corresponding electric mode analyzer 4 and the second input of the correction device 5, the second input of the time setting block 3 gov connected to the first output of the correction device 5, which is also coupled to the data input of the second switch 7 in its phase control circuit, the output of unit 14 specifying the dead zone is connected to the first input threshold specifying unit 3, four you (A

four

to

four

00

, the progress of each block 3 setting thresholds is connected to four inputs (second, third, fourth and fifth) of the electric mode analyzer A corresponding to this particular FY, and the sixth input of the last is connected to the output of sensor 2 of the arc voltage of the same phase, four outputs of the analyzer 4 electric mode connected to

corresponding to one of the twelve inputs of the generator 13 prohibitions, the third output of each analyzer 4 electrical mode is also connected to the input of the corresponding block 3 for setting thresholds, the first output of the generator of prohibition 13 is connected to the control input of the first key in the control circuit of phase A, the information

the input of which is connected to the second output 2Q of the switch 36 with the key element of the connecting device 5 of phase A, the third input of which is connected to the output of the sensor 11 current of the motor core and the fourth input is connected to

den with the output of the third comparator 25 and the input of the single vibrator 28, the first input of the third comparator 25 is connected to the output of the fourth comparator output of the rotation speed sensor 12, 25 P 23, the first input of which is connected to the second output of the imager 13 and prevents the output of the first filter 20

It is connected to the control input of the second key 7 in the control circuit of phase A, the outputs of the keys 6 and 7 are connected to the first and second inputs of the controller 8 of the power (-current) of phase A, the output of the latter is connected to the input of the thyristor unit 9, and the output of the unit 9 thyristors are connected to motor 10 of phase A, the third and quarter outputs of the inhibitor 13 are connected in a similar way to similar blocks of the control circuit of phase B, and the fifth and sixth outputs of the generator of the 13 inhibitions are connected in a similar way to analogous blocks of the control circuit of phase C.

The correction device 5 contains four adders 16–19, two filters 20 and 21, the comparators 22–27, one-shot 28, three reference voltage sources 29–31, a comparator 32 with a latch, two one-half-time rectifiers 33 and 34, A sample-storage device 35 (VHF), two amplifiers 36 and 37 with a key element, wherein the inverting input of the first adder 16 and the non-inverting input of the second adder 17 are interconnected and are the first input of the correcting device 5, the non-inverting input of the first adder 16 is connected to the first input. 22 comparator, the first input of the comparator 32 with a latch, iinverti

pyromHNOi inputs of the third and fourth adders 18 and 19 and is the second input of the correction device 5, the output of the first adder 16 is connected to the input of the first single-half rectifier 33, the output of which is connected to the information input of the first amplifier 36 with a key element whose output is connected to the first input of the VHR 35 and the first input of the second comparator 26, the first control input of the first amplifier 36 with the key element is connected to the second input of the VHR 35 and the output of the first comparator 22, the second input of which is connected to the output ervogo source 29, a reference voltage, a second control input of the first usidish yield third comparator 25 and the input of monostable multivibrator 28, a first input of the third comparator 25 is connected to the output of the fourth komparato30

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five

The pins are with the output of the second voltage source 30, the input of the first filter is the third input of the correction device 5, the second input of the third comparator 25 is connected to the output of the fifth comparator 24, the first input of which is the fourth input of the corrective device 5, the second input of the fifth comparator 24 is connected to the output of the third source 31 of the reference voltage; the third control input of the first amplifier 36 is connected to the key element with the output of the sixth comparator 27, to the third input of the water economy department 35 and the second input of the comparator with a latch 32, the fourth input of the VHD 35 is connected to the output of the second filter 21, the fifth input of the VHD 35 is connected to the output of a single vibrator 28, the sixth input of the UHT 35 is connected to the output of the second comparator 26, to the first control input of the second amplifier 37 with a key element and the output of the sixth comparator 27, the output of the WCX 35 is connected to the second input of the second comparator 26 and the inverting input of the second adder 17, the output of which is connected to the inverting input of the third adder 18, the third input of the comparator 32 with a snap 32 and tating device 5, the output of the third adder 18 is connected to

ten

the input of the second half-wave top section 34, the output of which is connected to the information1 input of the second amplifier 37 with the key element,. the second control input of which is connected to the output of the comparator 32 with a latch, and the output connected to the input of the second filter 21 and the inverting input of the fourth adder 19, the output of which is the second output of the correction device 5.

The device works as follows.

The signal from the third output of the electric mode analyzer 4 goes to the second input of the threshold setting unit 3, the arc current setting signal from the first output of the corrective device 5 of the device 3, the third input of the threshold setting unit 3, the first inputs of the threshold setting units 3 from output G of block 14, assignment of the dead zone. At the four outputs of each block 3 of the thresholds, signals are formed that are proportional to the minimum arc current at the first output; on the second output to the lower threshold of the insensitivity zone of the arc current IH-T at the third output to the upper threshold of the insensitivity zone of the arc current, on the fourth code the maximum allowed arc current IM «K.C

25

thirty

These four signals of each phase unit 3 set thresholds are fed to the second, third, fourth and fifth inputs of the corresponding phase analyzer 4 electrical mode, the first input of which receives a signal from the output of sensor 1 of the arc current I of the same phase, and the sixth input - the signal from the output of the arc voltage 2 of the same phase UoB of the electric mode analyzer 4 compares the magnitude of the current and arc voltage with the given thresholds for current and voltage Uon and the logical signals are generated at the output: first input - short circuit do 7); the second input is the contact of the charge (and j the third output is the arc current is in the dead zone (1st) the fourth output is the arc break ().

Signals from analyzer outputs 4

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50

; The second input of the first key to the pi phase B receives a signal from the second output of the phase B correction device, and the second input of the first key 6 in the phase C circuit - from the first output of the correction device 5 to the phase C circuit.

The second inputs of the second switches 7 of the phase circuits B and C are supplied with signals from the first outputs of the correcting phase B and phase C devices, respectively. The first inputs of the correcting devices 5 receive the arc current setting signal from the output of the arc current setting unit 15, to BTopoii ho ;; the corrective device 5 is cc1); ws the output of the arc current sensor 1 corresponding to the phase sensor 1. The third input of the correction device 5 receives a signal from the output of the corresponding motor current sensor 11, and a quarter input - a signal from the output of the corresponding speed sensor 12

The correction device 5 performs the correction of the signal of the arc current and the current sensor signal

5g electric mode (all three phases) if at the moment of contact

arrive at twelve entrances of the single-electrode electrode of the current arc less

The worldlord of 13 prohibitions, which is the for-set value and the engine Yu

obeys bans on the movement of electro-start work on the support

0

g Q

five

0

five

0

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0

Dov depending on the state of the electric mode of the arc furnace. ,

The signal from the first output (prohibition of the movement of the electrode of the phase A up) of the inhibitor driver 13 is fed to the control input of the first key 6 of phase A, to the information input of which a signal is received from the second output of the phase A correction device.

From the second output of the driver 13 prohibitions, the signal (the prohibition of the movement of the electrode of the phase A downwards) is sent to the control input of the second key 7 of the phase A, to the information input of which a signal is received from the second output. corrective device 5.

From the third and fourth formates of the 13 prohibitions, signals are sent to the control inputs of the first 6 and second 7 keys of the phase B circuit.

From the fifth and sixth outputs of the driver 13 of the prohibitions, the signals arrive at the control inputs of the first 6 and second 7 keys of the phase C, respectively.

; The second input of the first key in the phase B circuit receives a signal from the second output of the phase B correction device, and the second input of the first key 6 in the phase C circuit is received from the first output of the correction device 5 in the phase C circuit.

The second inputs of the second switches 7 of the phase circuits B and C are supplied with signals from the first outputs of the correcting devices of phase B and phase C, respectively. The first inputs of the correcting devices 5 receive a signal for setting the arc current from the output of block 15 for setting the arc current, to BTopoii xo ;; the corrective device 5 - sig) 1; w from the output of the arc current sensor 1 corresponding to the phase of the sensor 1. The third input of the correction device 5 receives the i signal from the output of the corresponding motor current sensor 11, and the quarter input receives the signal from the output of the corresponding speed sensor 12.

The correction device 5 performs the correction of the signal of the arc current and the signal of the current sensor du10

71A92489

The signal from the output of the first key 6 is fed to the first input of the corresponding phase power regulator 8, the second input of which receives a signal from the output of the second key 7 in the circuit of the same phase.

The phase power regulator 8, depending on the magnitude of the arc current signals and setting the arc current, generates a control signal for lifting or lowering the electrode, which then enters the input of the corresponding thyristor block, where it is amplified and 1c BiJbcoAa of the thyristor block 9 is fed to the corresponding motor 1 (J. Corrective device 5 operates as follows.

The inverting input of the adder 16 receives a signal from the block 15 of the set-NIN arc current, and the inverting input of the adder 16 receives a signal from the sensor of the arc current 1. The output of the adder 16 according to the formula

eight

,five

/ II

1, there is a deviation 41 of the actual arc current 1 relative to the setpoint 1. Next, the magnitude and output of the adder 16 is fed to the input of the first half-wave microphone of the 33, the output of which has only the negative component H1, which is then fed to the information input of the first amplifier 36 with a key element.

Thus, at the output of the first half-wave rectifier 33, the signal appears only if the arc current is less than the specified value. Further, the quantity / II multiplied by the gain factor k of the first amplifier 36 with a key element, from the output of the latter, is fed to the first input of the VHH 35. The value of k 4l is in fact a correction effect on the arc current command. The magnitude of this corrective action is remembered by the VHF 35 and further subtracted from the signal for setting the arc current I- according to the formula

the input of which receives the signal k-ui from the output of the WCS 35, and the non-inverting input receives the signal from the output of the unit 15 for setting the arc current. Next, the corrected value of the arc current I setting — from the output of the second adder 17 — notry — to the inverting input of the third adder 18, the third input of the comparator 32 with a latch, the information input of the second key 7 in the control circuit of its phase, and the second input of the block 3 that sets the thresholds of its phase.

The amplifier 36 with the key element is in the conducting state if there is no negative potential at the three control inputs, i.e. in the case of a current-arc (controlled by the first comparator 22); the operation of the motor body on the support (controlled by the third 25, fourth 23 and fifth 24 comparators and the first filter 20); UVH 35 operation in mode

25 samples (controlled by the second comparator 26).

The input of the first comparator 22 receives a signal from the sensor 1 arc current. In the case of arc current on

At the output of the first comparator, a positive potential is present, otherwise, in the event of a break in the arc, a negative potential appears at the output of the comparator 22.

35

40

45

The input of the first filter 20 receives a signal from the output of the sensor 11 of the motor current. The filter is needed in order to build up from the high-frequency pulsations of the current of the motor core and inrush currents. The smoothed current signal of the motor core from the output of the first filter 20 is fed to the first input of the fourth comparator 23, which is compared with the response threshold, which is set using the second source 30 of the reference voltage and corresponds to the current of the motor stop. Next, the signal from the output of the fourth comparator 23 is fed to the first input of the third comparator 25. The second input of the last receives a signal from the output of the fifth comparator 24, the first input of which receives a signal from the speed sensor 12. P I

I J-.

(2)

where I l is the corrected value i of the arc current setting.

The subtraction operation implies the second adder 17, which inverts

eight

The input of the first filter 20 receives a signal from the output of the sensor 11 of the motor current. The filter is needed in order to build up from the high-frequency pulsations of the current of the motor core and inrush currents. The smoothed current signal of the motor core from the output of the first filter 20 is fed to the first input of the fourth comparator 23, which is compared with the response threshold, which is set using the second source 30 of the reference voltage and corresponds to the current of the motor stop. Next, the signal from the output of the fourth comparator 23 is fed to the first input of the third comparator 25. The second input of the last receives a signal from the output of the fifth comparator 24, the first input of which receives a signal from the speed sensor 12. The fifth comparator monitors the presence of the signal from the speed sensor 12, i.e. rotation of the rotor of the engine 10. If there is a motor stop current and there is a signal from the speed sensor 12, a positive potential is present at the output of the third comparator 25, and in the remaining cases the output of the third comparator 25 is negative potential. The signal from the output of the third comparator 25 is fed to the second control input of the first amplifier 36 with a key element and the input of the one-shot 28. As the engine starts to work on the stop, the output of the third comparator 25 shows a positive potential, which will give permission for the signal to pass through the first amplifier 36 with a key element and will launch a single-vibration / 8, which produces a single Impulse of negative polarity arriving at the fifth input of the VHX 35. This pulse resets the previously stored value of the correct impacting and UVH 35 is ready to remember the new value of the corrective action.

... The second input of the second comparator 26 receives a signal from the output of the water economy department 35, and the first input receives a signal at the input of the water economy department. From the output of the second comparator 26, the signal goes to r the sixth input of the VHR 35, the input of the sixth comparator 27 and the first control input of the second amplifier 37 with a key element. The sixth comparator 27 inverts the output signal of the second comparator 26. The signal from the output of the sixth comparator 27 is connected to the third control input of the first amplifier 36 with a key element, the third input of the water economy department, the second input of the comparator 32 with a latch. If the signal at the first input of the VHR 35 (i.e., at the first input of the second comparator 26) exceeds or is equal to the signal at the output of the VHR 35 (i.e., at the second input of the second comparator 26), a negative potential is present at the output of the second comparator 26 the output of the sixth comparator is a positive potential, i.e. The VHX 35 is in the sampling mode, on the third control input of the first amplifier 36 with a key element there is permission to pass the signal, on the first control input of the second amplifier 37 with a key element a ban on signal passing, on the second input of the comparator 32 with a latch - ban on the work of the last. At the output of the comparator 32

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0

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0

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in this case, the latch has a negative potential, which then goes to the second control input of the second amplifier 37 with a key element, preventing the signal from passing through the latter. As soon as the signal at the output of the VHR 35 exceeds the signal at the first input of the VHR 35, the output of the second comparator 26 leads to a positive potential, the output of the sixth comparator has a negative potential. As a result, the VHR 35 switches to the Storage mode, at the third control input of the first amplifier 36 with a key element, it prohibits the passage of a signal through the last, at the first control input of the second amplifier 37 with a key element — permission to pass the signal through the last one, at the first input of the comparator 32 with a latch - e work of the latter.

Correction of the arc current is carried out in the following way.

If the arc current is less than the specified value at the moment of contact with the charge electrode, the motor stops 10, a correction effect k appears, and the water economy Department 35 remembers the latter. Next, the arc current is corrected downwards by the correction effect (2).

The values of the coefficient k are determined on the basis of specific requirements for the smelting technology and can vary from 1 to 2. With smaller values of k, the melting is carried out at short arcs by a stronger current, i.e. faster, but with increased carbon transfer to the melt. For large values of k, melting leads to longer arcs with less current and less carbon transfer from the electrodes to the melt.

Correction of the arc current is as follows.

The inverting input of the third adder 18 receives the signal for setting the arc current from the output of the second adder 17, and the non-inverting input receives the signal from the arc current sensor 1. The output of the third adder 18 according to the formula

.41 I - I j, (3)

we have a deviation of 41 actual currents of the arc I f from the given value of l.

The signal from the code of the third adder is fed to the input of the second one-half-period rectifier 34, at the output of which we have only the positive component of the deviation of the arc current from the specified value. The signal from the output of the second half-wave edge of the miter 34 is fed to the information input of the second amplifier 37 with a key element, the gain of which is 1. At the first control input of the second amplifier 37 with a key element, the inhibit signal is removed when the UV5 is in Storage mode. At the second control input of the second amplifier 37 with the key element, the inhibiting signal is removed by a comparator 32 with a latch, the conditions for which are as follows. When the VHR 35 switches to the Storage mode, the comparator receives a work permit and begins comparing the signals of the arc current and the task; arc current. At the moment of transfer of the VHX 35 to the Storage mode, the arc current is set to correct, which becomes less than the current flowing when the electrode touches the stitching, i.e. The power regulator 8, after practicing the disturbance that has arisen, will begin to move the electrode upward, reducing the arc current. At the moment of equality of the signals of the arc current TA and set the arc current

I

I comparator 32 with a 31 latch switches and locks (locks), i.e. Regardless of the magnitude of the signals at the first and third inputs, there is a positive potential at the output, which is allowed to pass the signal through the second amplifier 37 with a key element. The signal from the output of the latter arrives. on the 5th pass of the second filter 21 and the inverting input of the fourth adder 19, the non-inverting input of which receives a signal from the arc current sensor 1. At the output of the fourth adder 1 we have the corrected value of the arc current 1ph according to the formula

1F

 and

(four)

Thus, in the case of correction and installation of a new arc current setting, when the arc current is equal to a given value, the signal from the arc current sensor 1 is corrected by subtracting from it a positive

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component of the deviation of the arc current signal from a predetermined value.

In case of further deterioration of the arc burning condition, the power regulator 7 processes the disturbance in the following mode, moving the electrode down, and in the case of improving the arc burning conditions, the electrode does not rise upward, i.e. the melting process is more intense.

The second filter 21, to the input of which a signal comes from the output of the second amplifier 37 with a key element, is necessary in order to separate itself from the high-frequency pulsations of the arc current. The signal from the output of the second filter is fed to the fourth input of the VHR 35 and controls the magnitude of the corrective action, controlling the discharge of the capacitor C in the VHR 35. At the moment when the magnitude of the corrective action becomes zero, the VHR 35 switches to the sampling mode I,; 1 1F and control of the electric mode of the electric arc furnace is conducted in the usual way.

The device allows to increase the performance of an electric arc furnace and to reduce the specific energy consumption in the case of melting of the charge with low conductivity by reducing the time of charge melting. This is achieved by automatically selecting the optimum melting current and increasing it to the nominal value as the arc conditions improve.

Claims (1)

Invention Formula A device for controlling the electric mode of a three-phase electric arc furnace, containing in the control circuit of each phase a current sensor and arc voltage sensor, threshold setting unit, electric mode analyzer f, two switches, arc power controller (current), thyristor unit, actuator the form of an electric motor equipped with a speed sensor and a current sensor - a motor core, common to all phases of the deadband setting unit, arc current setting unit and prohibition generator, the current sensor output the arcs of each phase are connected to the first input of the corresponding / l electrical mode analyzer, the output of the deadband task unit is connected to the first input of each threshold setting unit, four outputs of each of which are connected to the BTopibiM - the fifth inputs of the corresponding phase analyzer of the electric mode, the sixth input of which connected to the output of the arc voltage sensor of the same phase, the output circuit of each electrical mode analyzer is connected to the corresponding inputs of the inhibitor, the third output to Each electrical mode analyzer is also connected to the second input of the corresponding threshold setting unit, each and a pair of the inhibitor generator outputs are connected respectively to the inputs of the first and second keys of each phase, the outputs of which are connected to the inputs of the phase power controller connected to the phase actuator , characterized in that, in order to increase productivity and reduce specific energy consumption by reducing the time of charge melting, into the control circuit of each f The basics additionally introduced a correction device containing four combiners, two filters, just the comparators, a single vibrator, three sources of reference voltage, a comparator with a latch, two single-pole rectifiers, a sampling-storage device (UHF), two amplifiers with a key element, and interconnected inverting input of the first adder and non-in; the rotating input of the second adder is the first input of the correcting device, which is connected to the output of the current setting unit, non-inverting the input of the first adder (connected to the first input of the first comparator, the first input of the comparator with a latch., the inverting inputs of the third and fourth adders and is the second input box - 1 - „ A rectifying device that is connected to the output of a current token sensor, the output of the first adder is connected to the input of the first one-half-one rectifier, the output of which 1 is connected to the information input of the first amplifier with a key element whose input is connected to the first input of the VHD and the first input of the second comparator first control input 0 five the first amplifier with a key element is connected to the second input of the WCH and the output of the first comparator, the second input of which is connected to the output of the first source of reference voltage; the second control input of the first amplifier with the key element is connected to the output of the third comparator and the single vibrator input; the first input of the third comparator is connected with the output of the fourth comparator, the first input of which is connected to the output of the first filter, and the second input - to the output 5 of the second source of reference voltage, the input of the first filter is the third input of the correction device, which is connected to the output of the current sensor motor current of this phase, the second input of the third comparator is connected to the output of the fifth comparator, the nepBbrfi input of which is the input of the correction device connected to the output of a speed sensor motor of this phase, the second input of the fifth comparator is connected to the output of a third reference voltage source, the third control input of the first amplifier with a key element the entrances are connected to the output of the sixth comparator, the third input of the VHF and the second input of the comparator with a latch, the fourth input of the VHR is connected to the output of the second filter, the fifth input of the VHR - with the output of the one-vibrator with a glue element and the input of the sixth comparator, the output of the VHR - with the second input of the second comparator and the inverting input of the second adder, the output of which is connected to the inverter, - the input of the third adder, the third input of the comparator with a latch and is the first output of the correction device, KOTopbui is connected to the third input of the threshold setting unit and the information input of the second key of this phase, the output of the third adder is connected to the input of the second half-wave rectifier, the output of which is connected to the key element, the second control login 5 of which is connected to the output of the comparator with the latch, and the output - with; the input of the second filter and the inverting / fourth input of the fourth adder, 0 five 0 five 0 the course of which is the second outgoing connection with the information input home of the correction device, which is the first key of this phase.