SU731616A1 - Three-phase electric arc furnace power automatic regulator - Google Patents

Description

one

This invention relates to electrothermia.

A power regulator is known, which contains sensors for arc current, phase nanoparticles, sensors for releasing a nerve and derivative of an arc current, and a device for isolating a fictitious extremum of active power 1.

Also known is an automatic power regulator for a three-phase electric arc furnace, containing for each phase an adder, the inputs of which are connected to its current and voltage sensors and sensors for releasing a nerve and the derivative of the arc current of all three phases, a reference unit, one input of which is connected to a reference voltage block and the output is through the power amplifier with the mechanism for moving the electrode 2.

The disadvantage of these regulators is that they do not ensure the invariance of regulatory actions relative to disturbances in other phases, which reduces the quality of regulation.

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

For this, the regulator is equipped with a control voltage extraction unit, the first input of which is connected to the output of the adder, the second input - to the selection sensors of the first derivative of the arc current two

other phases, and the output is with the second input of the comparison unit.

The drawing shows a schematic diagram of the regulator for a single phase 5 furnace.

The automatic power regulator of an electric arc furnace contains a current sensor 1, sensors 2 and 3 of the first derivative of the arc current with respect to time, respectively, for the 1st and 2nd

10 phase, sensor 4 for isolating the first derivative of the arc current with respect to time for the 3rd phase, sensor 5 for phase voltage drop, accumulator 6 for arc voltage, block 7 for isolating arc control voltage, block

15 Comparison 8, reference 9 unit, power amplifier 10, electrode movement mechanism 11.

Consider the stress selection on an arc using the example of the 1st phase.

20 The voltage drop in the phase of the furnace circuit is determined by the expression

U, U ,, + L, - + M ,,

+ + A, 3- + ii ,,

(one)

at

(Ud1 - voltage on the arc;

Claims (2)

where L is the own inductance of the phase of the secondary current lead of the furnace; 12, - mutual inductances between phases 1 and 2, 1 and 3; - active co-motivation of the secondary current supply phase; ii, 2,3 - currents in the electrodes. Whence the voltage on the arc / 7 - // / - М L-Ri- - t- 1 -1 12 dfdt and - the current in the electrode received from the current sensor 1, for example, from current transformers; the first derivatives of the currents with respect to time, obtained by means of sensors 2 and 3 of the extraction of the first derivatives of the current. For example, with the help of Sov. Rogowski, installed on two phases (1st and 2nd). The first derivative of the current of the 3rd phase, determined by the expression, is obtained by summing the first derivatives of the current of the 1st and 2nd phase in sensor 4, made, for example, on an operational amplifier. The values of L, MIS, Afia, R are determined by a calculation-experimental method for a specific furnace installation. The signals taken from current sensor 1, sensors 2, 3, 4 of the first derivatives of the arc current over time and sensor 5 of the phase voltage drop according to expression (2) are fed to the inputs of the voltage accumulator 6 of the arc, made for example at an operational amplifier, the signal at the output of which is proportional to the voltage on the arc. A signal proportional to the arc voltage from the output of the adder 6 is fed to the input of the arc-control voltage extraction unit 7 (made, for example, from series-connected adders, the effective arc-control voltage selection and filter) to the other inputs proportional to the voltage drop from the mutual inductances and MIS with the opposite sign, compensating for the influence of other phases on the control voltage. With such a control voltage, the regulator is only responding to disturbances applied to the links of its own channel. From the output (3) and block 7, the control voltage is applied to one of the inputs of the comparison block. The reference to the controller is a reference voltage block 9, at the output of which the secondary voltage of the furnace transformer converts into a reference voltage corresponding to the rational mode for each voltage level. The error signal between the arc control voltage and the reference voltage from the output of the block 8 is fed to the power amplifier 10, where it is amplified and determined by polarity and transmitted to the actuator AND, which moves the electrode 12 to the direction of eliminating the disturbance. The proposed automatic power regulator ensures the invariance of the control actions of excitations of disturbances in other phases. The technical and economic efficiency of the proposed automatic power regulator is confirmed by the results of the operation of the regulator with reference voltage, which provides partial invariance of control actions with respect to disturbances in other phases. The use of the latter in the arc steel-smelting furnace DSP-200 reduces the duration of smelting by 2.3-2.8% and reduces the power consumption by 1.0-1.5%. The proposed invariant regulator can reduce the duration of smelting on heavy electric furnaces by 3-4% and reduce the power consumption by 2.0-2.5%. The invention The automatic power regulator of an arc three-phase electric furnace, containing for each phase an adder, the inputs of which are connected to its current and voltage sensors and sensors for selecting the first derivative of the arc current of all three phases, a reference unit, one input of which is connected to a reference voltage block and the output is through a power amplifier with an electrode moving mechanism, characterized in that, in order to improve the quality of regulation, it is equipped with a control voltage extraction unit, the first input of which is connected nen yield adder, the second input - to the sensors isolating the first derivative of the arc current of the other two phases, and an output - to a second input of the comparison unit. Sources of information taken into account in the examination 1. USSR author's certificate number 173348, cl. F 27 D 11/10, 1962. 2.Electrowarme Internation, X 1974, s. .