SU1385337A1 - Device for regulating power of electric arc steel melting furnace - Google Patents

Abstract

The invention relates to electrical engineering. The aim of the invention is to increase the productivity of the furnace by increasing the accuracy of setting the arc current corresponding to the maximum effective active power. The device is equipped with a unit 12 for determining the rational arc current connected to the outputs of the unit 4 for measuring and storing the supply voltage,

Description

Do

00; l

GARDEN CO

fie. J

This invention relates to electrothermal conditions.

The aim of the invention is to increase the productivity of an arc steel-smelting furnace by increasing the accuracy of determining and setting a rational arc current corresponding to the maximum active power.

1 shows a block diagram of the device; Fig. 2 is a functional block diagram for determining a rational arc current.

The device contains a voltage measuring transformer 1 installed up to the furnace 2 switch on the high voltage side of the furnace transformer 3, measuring unit 4 And storing the voltage on the furnace supply buses, the jcoToporo input is connected to the output of the measuring transformer i voltage via a switch 5, united through the block 6 of matching with the furnace switch 2, the block 7 determining the short-circuit of the M01 CHARACTERISTICS network 5 blocks 8 calculating the transformation ratio of the furnace transformer 3, inductive 9 and full 10 resistances of the furnace circuit, the outputs of which are connected to voltage levels 11 furnace transformer 3, unit 12 for determining the rational current, an arc whose inputs are connected to the outputs of unit 4 for measuring and storing the voltage on 1 power supply lines of the furnace, unit 7 for determining the short circuit power of the network, b 8 of the transformation ratio of the furnace transformer 3, the calculating blocks of the inductive 9 and the full 10 resistances of the furnace circuit, and the output to the input of the unit 13 for setting the rational arc current, the comparison unit 14 connected by the output to the optional electrode moving mechanism 15 in the bath 17 of the furnace, inlets to the current sensors 18 of the arc, voltage 19 of the arc and block 13 of the task of a rational arc current.

Block 12 for determining the rational arc current can be performed according to the functional diagram (FIG. 2). Block 7 for determining the short circuit power (Bx.4) is connected to the input of the divider body 20, to which another input through the large-scale amplifier 21 is connected to inductive calculation block 9 furnace circuit resistance,

corresponding to the rational furnace mode (Bx, 2), the outputs of the blocks for calculating the transformation ratio 8 (Bx, 3) and calculating the impedance of the furnace circuit 10 (Bx, 1) are connected to the inputs of the multiplier 22, the output of which is connected to one BXOCt multiplier 23, another input which is connected to the output of the divider 20. The output of the multiplier 23 is connected to one input of the divider 24, the other input of which through a large-scale amplifier 25 is connected to the output of the unit 4 for measuring and memorizing the voltage on the power buses of the furnace (In 5). The output of the divider 24 is connected to both the input of the large-scale amplifier 26, which functions as an inverter, as well. and with the input of the quadrant 27, the output of which is connected to one of the inputs of the adder 28, the other input of which is connected to the output of the divider 20. The output of the adder 28 is connected to the input of the square root determination unit 29, the output of which is connected to one of the inputs of the adder 30, the other input of the Last connected to the output of the scale amplifier 26.

The device works in the following way.

In accordance with the position of the switch 11 secondary voltage levels in the calculating units of the transformation ratio 8, inductive 9 and full 10 resistances of the furnace circuit, the transmission coefficients for the selected stage are set, and the signals proportional to them are fed to the unit 12 for determining the rational arc current.

When the furnace switch 2 is turned off in the measurement unit 4 and the voltage is memorized, a signal proportional to the mains voltage is generated on the furnace supply buses connected to the measuring transformer 1, and together with the signal from the short power detection unit 7 network closure is also fed to block 12 for determining the rational arc current, from where the signal as a value for the rational arc current goes to block 13 for specifying the rational arc current, and then to block 14 for comparison, preparing a Str Torr furnace power for operation.

When the switch of the furnace 2 is turned on, the voltage measuring and storing unit 4 is turned off, and the fixed voltage value allows the current arc current unit 13 to maintain the current value unchanged until the next rise

electrodes with arc opening and switching off the switch.

The device realizes the definition and setting of rational current in accordance with the expression

-RZ

, W.S.S.

  Tfi - iif, ref

and

f.IC

phase voltage on the power busbars of the electric arc furnace (on the side of the primary winding of the furnace transformer) prior to its connection;

zi

Coxp X,

and

n

-

-u7

V g: V

  to

X. short-circuit power on the power supply bars of the electric arc furnace; inductive impedance of the network before powering the arc steel furnace; nominal mains voltage}

transformation ratio of the furnace transformer for the selected secondary voltage level Uj;

U

h / j1

+ Zk

inductive resistance of the furnace circuit, corresponding to the rational mode of the furnace, calculated by the values of active - g, inductive - X, full - Z resistances of the furnace circuit in the operating short circuit mode of the furnace}

+ rjVx

rac

-full resistance of the furnace circuit, corresponding to the rational mode of the furnace.

The calculation of the rational current is performed in block 12 ,, short-circuit power - in block 7, resistance X "(, c - in block 9, resistance Z

paç

rac

block 10.

S KZ Den

T, Gd

pa f

rats K. S.Bcn

pan Uiqi suit

15

20

25

The device performs the determination and maintenance in the furnace of a rational arc current corresponding to the maximum effective active power, taking into account the network parameters and the actual parameters of the furnace circuit at all technological stages and for all secondary voltage levels of the furnace transformer.

Claims (1)

Invention Formula A device for controlling the power of an electric steel-smelting furnace containing a high-voltage switch connected on the primary side of a furnace transformer equipped with a voltage level switch, in each phase of the furnace there is a current sensor and 30 voltage sensor connected respectively to the first and second inputs of the comparison unit, the third input of which is connected to the output of the rational arc current setting unit, and output 35 to the input of the actuator of the electrode movement, characterized in that, in order to increase the furnace performance accuracy of task 40 of rational arc current corresponding to the maximum active active power, it is additionally equipped with a power supply voltage measuring transformer, a key, a block 45 matching, measuring unit and storing a voltage, a network short-circuit power determining unit, a transformation ratio calculating unit, a Ductating Injection resistance calculating unit, an impedance calculating unit, and an rational arc current determining unit, the output of which is connected to the input of the rational arc current setting unit 55, the first input with output the impedance calculation unit, the second input — with the output unit inductive impedance calculation, the third input is with the output of the unit calculation of the transformation ratio, the fourth input - with the output of the network short-circuit power determining unit, the fifth input through the sequentially connected voltage measuring and storing unit and the key - with the output of the measuring voltage transformer, the control input the key is connected to the auxiliary contacts of the high-voltage switch through the matching unit; FIG. g