SU873473A1 - Three-phase electric arc furnace power regulator - Google Patents

Description

(54) REGULATOR OF ARBITNESS ARCH TRBB PHASE ELECTRIC OVENS

, one -. The invention relates to electrotherms.,

A device is known that contains in the control circuit of each phase current sensors and arc voltages, a comparison block V, a reference unit, an amplifier motor for moving an electrode, a unit for determining the furnace phase with the maximum deviation of the electric mode from the specified 1.

The disadvantages of this device are the alternate regulation of the electrical modes of the individual phases, which leads to additional electricity costs for melting to increase the duration of melting / a; Also, power control due to inaccurate determination of arc voltage is not sufficient. .

Also known is the power regulator of an arc three-phase electric furnace supporting for each phase an arc voltage detecting unit connected to the first input of the comparator unit, the second input of which is connected to the reference unit and the output to the electrode displacement motor equipped with a speed sensor connected to the input block calculating the first derivative of the speed, the output of which

connected to the input of the threshold evil 21,

The disadvantages of such a device are the poor quality of regulation due to the non-authenticity of the regulation of the electrical modes of individual phases.

The purpose of the invention is to improve the quality of regulation.

ten

The goal is achieved by the fact that the controller is equipped with a block for detecting a simultaneous break of three arcs, one output of which is connected to the control inputs of the entered two keys,

15 connecting: the inputs of the comparison block with the block; the arc voltage definition and the block of the task; the second output of the Block Detection of three arcs is connected to one of the inputs of the coincidence element and through the third key - with

20 by the first control input of the fourth key connecting the output of the comparison unit with the electrode displacement motor, the second control center of the fourth key is connected to the output of the threshold element, and the control input of the third key is connected to the output of the matching element, the other three inputs of which are connected to the outputs unit display off the oven.

thirty

The block for detecting the simultaneous break of three arcs contains current sensors of three phases, each of which is connected via a display element zero to the input of the second coincidence element, the output of which serves as the output of the specified block.

The kiln switch-off indication unit contains three phase voltage sensors, each of which is connected to the input of the zero indication element, and the outputs of all elements serve as outputs of the indicated kiln-off indication block.

FIG. 1 is a block diagram of the controller; in fig. 2 is a schematic implementation of a three-arc break detection unit; in fig. 3 is a schematic implementation of the furnace disconnection indication unit.

The power regulator for an electric arc furnace contains a unit for detecting voltage on arc 1, a comparison unit 2, a reference unit 3, an amplifier 4, a motor moving an electrode 5, a motor speed sensor 6 a block for calculating the derivative of the motor speed 7, a threshold element 8, a block for detecting a simultaneous breakage of three arcs 9, a unit for detecting a shutdown of the furnace 10, keys 11-14, switching unit 15, a coincidence element 16. A block for detecting a simultaneous breakage of three arcs contains current sensors of three arcs 1719 display elements zero 20-22, element nt coincidence 23. The furnace disconnect indication block contains voltage transformers 24-26 / whose primary winding is connected between the electrode holder terminal and the pin bogged down in the hearth for each furnace phase, display elements zero 27-29.

The power regulator for an electric arc furnace works as follows. .

When the furnace is turned on when the arcs are hot, a signal appears at the output of the unit to detect the simultaneous breakage of three arcs 9, which locks the keys 11 and 12 and, affecting the switch 15 through the open key 14 | applies the nominal voltage to the bark of the motor moving the electrode 5. The key 13 is open. The motor for moving the electrodes 5 moves the electrodes until they come into contact with the charge. At the moment of contact of the first electrode with the charge, the signal from the unit for calculating the derivative of the engine speed 7 increases the set point of the threshold element 8 and locks key 13. When the second electrode reaches the charge, a current occurs in the circuit, which causes unit 11 and 12 to turn off. In this case, the signal from the unit to determine the voltage

arc 1 through the switch 11 enters the input of the comparator unit 2, where it is compared with the setpoint voltage that comes from the task block 3 through the switch 12. The signal of the difference between these signals comes from the output of the block 2 to the input of the amplifier 4 and further to the motor moving the electrode 5. The motor moves the electrode until the voltage across the arc becomes equal to the specified value.

If the furnace is turned off, the signal from the output of the block detecting the simultaneous breakage of three arcs 9 enters the input of the block of the coincidence element 16. As a result of the currents and voltages at the arcs in this case equal to zero, the output of element 16 is a signal that locks the key 14, which prevents the movement of the electrode.

The proposed power regulator for electric arc furnaces allows autonomous control of the electrical mode of individual phases, which leads to a decrease in the wear of the mechanical parts of the electrode drive. The economic effect from the introduction of the invention is 1 million 360 thousand rubles. in year.

Claims (2)

1. A power regulator for an arc three-phase electric furnace containing, for each phase, an arc voltage detection unit associated with the first input of the comparison unit, the second input of which is connected to the reference unit, and the output with the electrode displacement motor equipped with a speed sensor connected to the input the computing unit of the first derivative of the speed, the output of which is connected to the input of the threshold element, is designed so that, in order to improve the quality of regulation, it is equipped with a block for detecting the simultaneous breakage of three arcs, one output which is connected to the control inputs of the entered two keys connecting the inputs of the comparison unit with the arc voltage detection unit and the task block, the second output of the three arc break detection unit is connected to one of the matches element inputs and through the third key to the first control element the input of the fourth key connecting the output of the comparison unit with the electrode displacement motor, the second control input of the fourth key is connected to the output of the threshold element, and the control input of the third key is connected to the output of the element The three other inputs of which are connected to the outputs of the furnace off indication unit. 2. The regulator in clause 1, that is, that the block for detecting a simultaneous break of three arcs contains current sensors of three phases, each of which is connected via a display element zero to the input of the second coincidence element, the output of which serves as the output of the specified block. 3, the Regulator according to claim 1, wherein the furnace shut-off indication block contains three phase voltage sensors, each of which is connected to the input of the zero indication element, and the element outputs serve as outputs of the indicated furnace shut-off indication block. Sources of information taken in. attention during examination 1. Authors certificate of the USSR 192307, cl. H 05 B 7/148, 1964. 2. USSR author's certificate on application 2625201/07, cl. H 05 B 7/148, 06.26.78. hc27 zs Z8 GB Z9 J6