SU736387A1 - Device for automatic control of electrode furnace power - Google Patents

Description

(54) DEVICE FOR AUTOMATIC REGULATION OF POWER OF ELECTRODE FURNACE

I

The invention relates to electrothermal and can be used to automate the electrical mode of electrode furnaces of various types, in particular, in the abrasive industry for melting normal electro-corundum.

A device for controlling the power of an arc furnace containing current and voltage sensors, an amplifier, an executive motor, a motor speed sensor, a feedback voltage divider, and a nonlinear resistance controlled depending on the furnace parameters, made on a transistor with an emitter-base input, is known. and collector-base output 1.

A disadvantage of this device is the poor quality of the adjustment.

The closest to the technical essence of the present invention is a device for automatic regulation of the electric mode of an electrode furnace, containing for each furnace a current sensor connected to one input of the comparator unit, the second input of which is connected to the output of the adjustable reference node, and the output to the engine regulator

electrode displacement, logarithmic current and voltage transducers, null organ and voltage step switch of the power transformer 2.

However, this device does not provide optimal power control, resulting in reduced furnace performance.

In order to increase the furnace performance, the outputs of these current and voltage transducers are connected in series and counter and connected to the first time relay input, the second input of which is connected to the output of the step change unit of the reference resistance, and the output through the zero a device whose output is connected to the inputs of the voltage step switch, the step change unit of the reference resistance, the reference node and the third time relay input.

The drawing shows a structural

20, the scheme of the proposed device for automatic power control of an electric arc furnace for one phase of the circuit for the other two phases is similar).

To B151voda power transformer 1 is connected to the electrodes 2 of the furnace. Current transformer 5 and phase voltage, respectively, are connected to the inputs; yugarif, converters 3 and 4. A stabilized voltage Lchev1- Reference resistance 6 is connected to the input of a stepwise change in the reference signal E5 lepi; the reference resistance 6 is connected with the switch of the reference resistance 7.

The outputs of logic converters 3 and 4 and the switching unit of the reference impedance 7 are connected in series and counter and loaded respectively at constant resistances 8, 9 and 10. The signal taken from these resistances is proportional to the change in the resistance of the melt and is fed through time relay 11, a null relay with the dead zone 12, the relay device 13 to the switch of the reference resistance 7, the switch of the voltage steps of the power transformer iodine load 14, the time relay II and the control unit 15, pi melting away (Jzem.

current transformer 16 is connected via a current converter 17 to one of the inputs of the comparison unit 18, the second input of which is connected to the reference node 15, and the output through the regulator 19, the relay device 20, the drive motor 21 to the interchange device: P1SNII electrode 22, kinematically connected connected with electrode 2.

The device works as follows.

At the beginning of melting, the adjustable reference node 15 is placed in the position in which it acts as a threshold device, and the signal to regulator 19 is supplied only to lift the electrode upwards (in the case of an increase in current, Faster than the maximum voltage of a power transformer for a given step). Since the phase resistance is maximal at the beginning of melting after charging into the furnace, the voltage step selector is in a position that provides the maximum voltage on the low side of the power transformer 1. As the melting point melts and therefore the phase resistance decreases, the signal is proportional to the resistance of the melt at the input of the time relay I, from where it arrives at the null relay with the dead zone 12. When the signal exceeds the sensitivity zone, the null relay turns on the relay oystvo 13 which delivers the signal to switch voltage levels. It switches the power transformer 1 to a lower voltage level. A relay device 13 controls a time relay 11, which, with a time delay, short-circuits the input of a null relay to prevent frequent switching of voltage stages of a power transformer, shifting the voltage of reference standard 7, which increases reference resistance 6 by

one section, controlled by reference} evil 15 for automatically changing the threshold value, corresponding to the maximum current of the power transformer for a given stage. If, after the end of the time delay of the relay 11, the signal at the input of the null relay exceeds the dead zone, then the process described above takes place until the signal at the input of the zero relay goes out of the dead zone.

As the melt accumulates in the furnace bath and, consequently, the current is higher than the maximum allowable for a given voltage step of the power transformer, the signal will be supplied to the electrode lift up from the current converter 17 through the threshold device of the node 15, the controller 19, the relay 20, the motor drive 21 to the device moving the electrode 22.

When the melt is completely melted and heated to a certain melt temperature, the voltage step selector switch is in a position where the voltage on the low side of power transformer 1 is minimal. This period of smelting is characterized by the fact that the process is

 melt to the desired concentration of A-fjpj and further heating before release. For smoother power control, at this time, node 15 is placed in a position whereby a current of a certain magnitude is maintained. The signal from the current transformer 16 through the current converter 17 is compared with the signal of the reference node 15 and the difference is fed to the controller 19, which through the relay device 20, the drive motor 21 and the device for moving the electrode 22 controls the position of the electrode 2, and therefore supports current at a given level.

The proposed device helps to optimize the power load of the power transformer of the furnace, reduce the melting time and, consequently, reduce heat losses, which, in turn, affects the reduction of specific power consumption and increase in labor productivity.

Claims (2)

1. USSR Author's Certificate No. 459716, cl. H 05 B 7/148, 1972. 2. Pirozhnikov V.E., et al., Automation of the control and management of electric steel-making units, M. Metallurgi, 1974, p. 172-2175.