SU1003391A1 - Device for control of electric mode of electric arc furnace - Google Patents

Description

An additional key block is connected between the second input of the first comparison block and the output of the first task block, and its control input is connected to the output of the first threshold element.

The drawing shows a power controller for an electric arc furnace.

The device contains an arc current sensor 1, an arc voltage sensor 2, blocks 3 and 4 of comparison, blocks 5

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6 tasks, commutation block 7, power supply unit 8, adjustable deadband unit 9, amplifier 10, electrode displacement engine 11, electrode movement speed sensor 12, threshold elements 13 and 14, coincidence element 15, key blocks 16 and 17.

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The device works as follows. .

A signal proportional to the arc current is supplied from the output of the arc current sensor 1 to the first input of the comparison unit.3, to the second input of which a signal is received from the task setting unit 5, proportional to the required arc current. When the electric mode of the furnace phase deviates from the set point at the output of the comparison unit 3, a signal appears that is proportional to the difference between the actual and set values of the arc current. This signal is fed to the switching unit 7 and then to the input of the block 9 of the adjustable deadband. The signal from the output of the block 9 through the amplifier 10 enters the motor 11 for moving the electrode, causing the required movement of the electrode.

When the arc is broken, the signal at the output of the threshold element 13 disappears. In this case, if the electrode is not in contact with the charge (melt J, then the signal at the output of sensor 2 on the arc voltage is greater than a predetermined threshold value and at the output of threshold device 14 a signal appears that goes to the second input of block 15 of coincidence. In In this case, a signal appears at the output of the element 15, which opens the key block 16 and, acting on the first control inputs, respectively, of the switching unit 7 and the power supply unit 8, starts the motor 11 for moving the electrode to the nominal voltage.

At the moment when the electrode speed is reached, measured by the electrode’s moving speed sensor 12, the switching speed value specified by the task block 6, a signal appears at the output of the reference block 4 and is fed through the open key block 16 to the second control inputs, respectively switching unit 7 and power supply unit 8

displacement of the electrode is supplied from the power supply unit 8, corresponding to the movement of the electrode with a steady speed equal to the switching speed. At the moment of contact of the electrode with the charge, a signal appears at the output of the arc current sensor 1, which leads to the disappearance of the signal at the output of the threshold device 13 and, accordingly, at the output of the coincidence element 15. As a result, the key block 16 is closed, and the control of the electric mode of the phase proceeds according to the difference of signals proportional to the actual and specified values of the arc current. If the arc voltage is less than a predetermined threshold value, for example, when three arcs are re-ignited, when one of the electrodes first touched the charge (melt) or when three arcs were broken, while one of the electrodes was in contact with the charge (melt) , the signal at the output of the threshold element 14 will be absent. In this case, the signal from the output of the threshold element 13, acting on the control input of the key block 17, closes it and the signal from the task block 5 does not arrive at the second input of the comparison block 3. As a result, the control signal on the motor 11 for moving the electrode will be absent, which will prevent unwanted movement of the electrode up or down until the melt mixture is in contact with another electrode. At the moment when the charge (melt) is reached, another phase current appears and the signal at the output of the threshold element 13 disappears. As a result, the key block 17 opens and the second input of the comparison unit 3 receives a signal from the task 5 block, i.e. from now on, the mode is based on the difference between the actual and specified values of the arc current.

The device makes it possible to increase the accuracy of furnace power control by switching to the control of the electric mode of the phases by a signal proportional to the arc current, which is accurately measured on electric arc furnaces.

As a result of testing a prototype of the proposed power controller on a DC-5MT MMZ Serp and Kolot arc steel-smelting furnace, it was found that the accuracy of maintaining a given furnace power increased by no less than 5%.

The overall expected economic effect. From the application of the proposed regulator on 100 ovens DO-5MT is 508.7 thousand rubles.

Claims (1)

Claim Device for controlling electric. tric mode of the electric arc furnace, containing a voltage sensor and a current sensor in the control circuit of each phase, connected to the first input of the first comparison unit, the second input of which is connected to the output of the first task unit, and the output is connected to the first input of the switching unit, second the swarm input of which is connected to the power supply, and the output through the block of adjustable aeons of insensitivity and the amplifier is connected to the electrode displacement motor, the electrode displacement speed sensor 15 connected to the first input of the second comparison unit, connected the second input with the output of the second task unit, and the output with the input of the key unit, the output -q of which is connected to the first control inputs of the switching unit and the power source, two threshold elements, the input of the first of which is connected to the current sensor, the second to the voltage sensor, and their outputs with inputs of the coincidence element, the output of which is connected to the control input of the key unit and the second control inputs of the switching unit and the power source, characterized in that, in order to improve the quality of regulation by increasing the accuracy of maintaining a given power during melting, it is equipped with an additional key unit included between the second input of the first comparison unit and the output of the first task unit, and its control input is connected to the output of the first threshold element.