SU731617A1 - Regulator of electric operating mode of steel-melting electric arc furnace - Google Patents

Description

 one

This invention relates to electrothermal conditions.

The arc electric furnace controller is known, which contains a current sensor connected via a rectifier to the first input of the comparator unit, the second input of which is connected to the reference unit and the output to the control unit of the mechanism for moving the electrode 1.

However, such a regulator does not provide automatic start-up of the furnace and rather stable regulation.

The closest to the technical essence of the invention is the electric mode regulator of an electric steel arc furnace containing for each phase a voltage step switch of a power transformer, an active power sensor, an active power setting unit equipped with two contacts a reversible zero organ, the inputs of which are connected to a sensor arc current and block arc current setpoint, and two amplifier 2.

However, this regulator does not allow power control in terms of ambiguity of the dependence of the power released in the arc on the arc current, as a result of which the electric costs of the furnace increase.

To improve the energy performance of the furnace, the proposed regulator is equipped with a potentiometer for setting active power, one output of which is connected 5 to an active power setting unit connected to the first input of the first amplifier, to the second input of which is connected a power sensor connected through the first contact of the reversible null organ with the first 10 input of the second amplifier, connected via the second contact of the zero-organ with the output of the first amplifier, the second VCh of the second amplifier is connected to the motor of the active setting oschnosti, the second terminal of which is grounded 15, and the gain of the first amplifier to the first input of twice Large Live than the second.

FIG. 1 is a block diagram of the proposed controller; in fig. 2 shows the operational and fictitious characteristics of the furnace, where P is the furnace power;

/ - furnace current;

25o-bc — upward branch of the operating characteristic of the furnace;

c-b-d-e-descending branch of the operating characteristic of transfer;

cd is fictitious branch of furnace characteristics;

Рmax - maximum of the discharge in the arc is active power and at this voltage level of the furnace transformer;

/ max is the arc current corresponding to the maximum active power released in the arc at a given stage of the furnace transformer;

РЗ is the specified value of the active traffic that is emitted in the arc;

1, /; / - arc current, corresponding to the specified value of the active power released in the arc on the upstream and downward branches of the furnace operating characteristic; Short-circuit short-circuit current;

Pta, Ptd - respectively, the furnace power is active at points a and d of the working characteristic of the furnace; fa, / d - respectively, the arc current at the points and the operating characteristics of the furnace. The controller contains a switch for the voltage steps of the power transformer 1, to the output of which are connected the inputs of unit 2 for setting the arc current corresponding to the maximum active power released in the arc, and block 3 for setting the active power. The inputs of the reverse nullorgan 4 are connected to the outputs of the arc current sensor 5 and the arc current setting unit 2, corresponding to the maximum active power output in dZg at this voltage level of the furnace transformer. The output of the active power reference unit 3 is connected to the first inverting input of the first amplifier bis with a potentiometer 7 of the active power reference. The output 8 of the active arc power sensor is connected to the second inverting input of the first amplifier 6 and through the contact 9 of the reverse null organ 4 to the digital inverting input of the second amplifier 10, the second input of the second amplifier is connected to the motor potentiometer 7 for setting the active arc power. The output of the first amplifier 6 through pin 11 is connected to the first input of the second amplifier.

The regulator works as follows.

Suppose that the furnace mode deviated from the specified RE. s in a way that is characterized by the point a of the operating characteristic of the furnace, where the current value of the power is Pta, and the arc current is / a. In view of the fact that the arc 1 / a is less than the current / max corresponding to the maximum of the active power Pmax in the arc at this voltage level of the furnace transformer, it turns out in the reverse zero-organ 4, which shows the sign of the difference / max - / a. closed contact 9 and open contact 11; at the same time, the first inverting input of the amplifier 10 is given a signal Pta-At the output of the amplifier 9, the error signal AP, which controls the movement of the electrode, is equal to

DR (). (1)

Under the influence of this signal, the electrode moves downward until the pumping mode returns to the point b (Pz, s) of the operating characteristic of the furnace.

If a short circuit occurs or the furnace mode deviates in such a way that is characterized by a point a of the operating characteristic of the furnace, the sign of the difference is opposite to the opposite, and in the reverse null organ 4 the contact is closed, and contact 9 is opened. When this output amplifier 6 signal is equal to

2R J

R / R.

 f l

2R b: (2 / max-I /. (2)

This signal is fed through the closed contact 11 of the reverse null organ 4 to the first inverting input of the amplifier 10, at the output of which the error control signal AP, controlling the movement of the electrode, is equal to:

(2I «ax-Yau 3 d- ()

Thus, instead of the signal - Ptd, the input of the amplifier 10 is given a signal defined by expression (4), which corresponds to replacing the downward branch of the furnace operating characteristic from point (Pmax / max) to point e with its mirror image relative to the ordinate (dotted line with -d-e). This eliminates the ambiguity of the working characteristic of the Yiechi. Under the influence of the signal AR, defined by expression (3), the regulator begins to displace the electrode up, and the operating

the point characterizing the operation of the furnace moves along the fictitious branch of the e-d-c characteristic to point c. After passing the point c, the sign of the difference in the arc current / max - / 3 is changed to the original, and the control signal is again determined by expression (1). The operating point, which characterizes the furnace mode, moves to the upstream branch of the operating characteristic of the oven, abc, and the controller returns it

at a given point b (Pz, / C)

When switching the voltage steps of the furnace transformer, the values of Rma-with AiaKc change. Therefore, during the transition of stages, the switch of the voltage levels of the furnace transformer acts on the unit 2 setting the arc current corresponding to the maximum output of active power in the arc and the block specifying the maximum output of the output arc of active power 3 so that they correspond to the arc voltage on each voltage steps of the furnace transformer.

The use of the proposed controller will increase the accuracy of maintaining the active power introduced into the furnace, which will approximately increase the productivity of the furnace by 0.5-1%. This will annually provide an increase in the production of high-quality steel by 1500-3000 tons for arc nets with a capacity of 100 tons.

Claims (2)

1. Electric mode regulator of an electric steel arc furnace containing for each phase a voltage transformer switch of a power transformer, an active power sensor, an active power setting unit, a reversible null organ equipped with two contacts, the inputs of which are connected to an arc current sensor and a current setting unit arc and two an amplifier, characterized in that, in order to improve the energy performance of the furnace, it is equipped with an active-power setting potentiometer, one output of which is connected to the active-setting power unit connected to the first input terminal; the first amplifier, to the second input of which a power sensor is connected, connected through the first contact of the reversing a null organ with a nerve input of the second amplifier connected via a second contact of a null organ with the output of the first amplifier; the second terminal of which is grounded, and the gain of the first amplifier on the first input is two times larger than on the second. 2. The regulator according to claim 1, about tl and h a y i and with By the fact that the inputs of the arcing current and active power units are connected to a voltage step switch. Sources of information taken into account in the examination 1. Svenchansky A.D. and others. Automatic control of electric furnaces. M., “Energie, 1965, p. 337. 2. G. Farsanov. Automation of processes of electric steel trays. M., “Metallurgists, 1972, p. 87 G, 1 7 | S rtCi: fl la i5 H J ma with jI (t / rj Rig. 2