SU1432809A1 - Automatic power regulator of steel-melting arc furnace for producing metallized pellets - Google Patents

Abstract

The invention relates to electrical engineering. The aim of the invention is to increase the reliability of operation of the furnace by increasing the accuracy of fixing the moment of the electrode stop to the charge. The magnitude of the ratio of the magnitudes of constants. The component currents of the arcs in different phases and by the sign of the constant components reliably establish the fact of a single-phase or two-phase short-circuit. To determine the three-phase short pulse, the three-phase current harmonic sensors are used, which allow to determine the fact of complete short circuit in the furnace by zero values of the higher harmonics of the arc currents simultaneously in all phases. As a result, it is possible to quickly respond to the charge falls and prevent the electrodes from breaking. 1 il. (L

Description

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CD

The invention relates to electrothermal, in particular, automatic power control of a three-phase electric arc furnace for smelting metallized pellets.

The purpose of the invention is to increase the reliability of the furnace by increasing the accuracy of fixing the moment of the electrode stop into the mixture.

The drawing shows a functional diagram of an automatic power controller of an electric steel-arc furnace.

The automatic power regulator of an arc steelmaking PR.CHI contains an arc current sensor 1 for each phase, a phase voltage sensor 2 for each phase, three sensors 3-5 constant component arc currents, three sensors 6-8 harmonics of arc currents, six amplifiers 9-14 DC, six inverters 15-20, six adders 21-26, six zero-organs 27-35, four logical elements And 36-39, six keys 40-45, six diodes 46-51, four logic elements OR 52-55, a recording device 56, a time relay 57, two blocks 58 and 59 of effective values in each phase of the gauges 60 power in each phase, the comparison unit 61 in each phase, the power amplifier 62 in each phase, the actuator 63 kazhdoy- phase, electrode 64 in each phase.

The arc current sensor 1 and the phase voltage sensor 2 are connected to the inputs of the respective blocks 58 and 59 of effective values. Sensors 3-5 of the constant component arc currents are connected to the inputs of the corresponding pair of amplifiers 9-10, 11-12, 13-14. The same outputs of sensors of constant components are connected to the corresponding pair — counter-connected diodes 4b-4 /, 48-49, 50-51.

In addition, the output of the DC component of the arc current 3 is connected to the corresponding inputs of the adders 21 and 22. The output of the sensor 4 is a constant component of the arc current connected to the corresponding inputs of the adders 23 and 24. The output of the sensor 5 DC component of the arc with the corresponding day inputs of the matrices 25 and 26. The other inputs of the adders 21-26 are connected via inverters 15-20 to the outputs of the amplifiers 11, 13, 9, 14, 12 and 10, respectively. Outputs

Q 5

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adders 21-26 are connected to the inputs of null organs 27-32, respectively. The outputs of each pair of null organs 27-28, 29-30, 31-32 are connected to two inputs of logic gates And 36-38, respectively. The outputs of the latter are connected to the corresponding key pair 40-41, 42-43, 44-45, the control inputs of which are connected to the diodes 46-51, respectively. The output of the key 40 is connected to one of the inputs of the logical element OR 52. The output of the key 41 is connected to the corresponding inputs of the logical elements of WIT 53 and 54. The output of the key 43 is connected to the corresponding inputs of the logical elements OR 52 and 54. The output of the key 44 is connected to the corresponding input of the logical element OR 54. The output of the key 45 is connected to the corresponding inputs of logical elements OR 52 and 53.

Sensors 6-8 harmonics are connected through zero-bodies 33-35 with the corresponding inputs of the logical element And 39. The output of the logical element And 39 is connected to the corresponding inputs of the logical elements OR 52-54. The outputs of these elements are connected to the corresponding inputs of the registering device 56 and three inputs of the logic element OR 55. The output of the logic element OR 55 is connected via a relay 57 of time of each phase to the corresponding input of the comparator unit 61, the other three inputs of which are connected to the outputs of the actuator me- Khanizm 63, block 58 effective values and with the output of the unit 60 power, the input of which is connected to the output of the block 59 effective values. The output of the 61 cpa unit is connected via a power amplifier 62 to the input of the actuator 63 for moving the electrode 64.

The regulator works as follows.

Signals from sensors 3-5 of the constant arc current components are amplified by amplifiers 9-14 with corresponding gain factors. The same signals from sensors 3-5 of the constant components of the arc currents are fed to one of the inputs of three pairs of adders 21-22, 23-24, 25-26. The signals from the outputs of the amplifiers 9-14 through the inverters 15-20 are fed to the other inputs of the corresponding adders, the signals from which are fed to the zero-organs 27-i

32, With zero voltages at the inputs of the zero-organs 27-32, signals appear at the outputs, which are received in pairs at the inputs of the three AND 36-38 logic elements. In the case of the presence of signals at both inputs of the And 36-38 elements, information from the output of each of them goes through the corresponding key pair 40-41, 42-43, 44-45 to the inputs of the corresponding Logical elements OR 52-54. The keys 40-45 are controlled via diodes 46-51, depending on the sign of the constant component of the arc current of one or another phase. The signals from sensors 6–8 harmonics of the arcs flow through the null organs 33–35 to the three inputs of the logic element I 39. With zero values of the signals on all outputs, yes: 6–8 harmonics, which is the case when the sinusoidal current is flowing ( three-phase short-circuit mode), at the output of the AND 39 element, a signal appears, which is fed to one of the inputs of the three elements OR 52-54. The signals from the outputs of the OR elements 52-54 are fed to the inputs of the registering device 56 and to the inputs of the OR element 55, the signal from its code enters the control system by moving the electrodes of each phase. For example, the signal from the output of the element OR 55 flows through the relay 57 of the time of the first phase to one of the inputs of the comparator unit 61, and from its output the voltage flows through the power snubber 62 to the actuator 63 of the displacement of the electrode 64 of the first phase. The signals from the current sensor 1 and the phase voltage sensor 2 through the power setpoint 60 and the effective value blocks 58 and 59 are fed to the corresponding inputs of the comparison unit 61. In addition, a signal from the actuator 63 arrives at one of the inputs of the latter. When studying the electromagnetic processes in the power supply system of arc steel-smelting furnaces on a digital model, it was found that if the arcs of the three phases are unbalanced, the arcs appear in the arc currents. For the case of a symmetrical power supply system or a three-phase short circuit, these constant components are absent.

In the case of single-phase and in the case of a two-phase short circuit, in one of the phases the maximum

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the value of the constant component (1d), and with a single-phase short circuit, the maximum constant component of a strictly defined polarity is in the same phase where a short lock occurs. The ratio of 10 to the constant components of the arc currents of other phases regardless of the voltage level of the furnace transformer is constant. In the case of a two-phase short scan, the maximum constant component of the arc current flows in the opposite direction to that in which the maximum constant is This is the case for single-phase short-circuits, with short-circuits taking place in those phases where the constant component of the current is not the maximum. Denote the ratios of the maximum values of the constant components of the currents of the arcs jjj to the constant components of the two other phases as follows: a, j; on, j, o k;

Jlom / j (o 3 jlpm / j

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/ J, o

 3 30m

ten

liem

thirty

/ J

 four

TO

h

J JOm

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ABOUT

oh oh oh

The values of K ,, - K depend on the type of electric arc furnace and are determined experimentally or with the help of a digital model.

A census is given to D, K, -K as follows:

1- If t

J torn 2o

-iion, - 30

Jlom

4 lorn 4Dev °

 J E from K j 5 O

Multiplication of constants

on the appropriate value is performed using amplifiers 9-14. Adders 21-26 determine the difference between the following values: j, 5 - J o J 20 3-3ffl J 10

Jso J o 5-3 th

Thus, if the maximum

the value of the constant component 1 is the place in the first phase, at the outputs of only null organs 27 and 28 a voltage appears, if in the second phase voltage appears at the output of zero organs 29 and 30, and if the maximum the value of the constant component takes place in the third phase, at the outlets only the null organs 31 and 32 show the voltage. If there is a current Ign t at the output of the logic element AND 36 a signal appears, if there is a current

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arc stress. To obtain information about the three-phase short circuit, signals from sensors 6-8 are used.

The liam signal appears at the output of the element And 37, and if 1zo at the output of the element 38, the elements And 36-38 serve as an indicator of the maximum en-r. current harmonics. With three phase short

the constant component of the phase currents. Depending on whether a two-phase or single-phase short-circuit takes place in the furnace will be different and

Note: there are no higher harmonic components in the arc currents and, therefore, with their zero values in three phases, which are controlled.

I / om signs. "Control of this implementation by null-bodies 33-35, is fixed using keys 40-45, controlled through diodes 46-51. For example, if a single-phase short circuit occurs in phase F-2, a signal appears at the output of element 36, the dp of which key 42 is open, because with such a short circuit the 1 oiri sign is negative and the diode 48 passes the opening signal of the key 42

the presence of a complete short circuit in an electric arc furnace. Thus, only in the case of a three-phase short circuit at the output of a logic element) And 39 a signal appears that goes to one of the inputs of all three, logical elements OR 52-54.

The regulator allows you to quickly respond to the collapse of the charge by raising the place of a two-phase short circuit-20 mz. electrodes and prevent breakage in phases F, and F, the signal from the output of the element I 37 passes through the key I 43, since in this case the sign Ijom; positive and through the diode 49 proiz-; opening of the given key goes 43.; In case of short circuit in; phase f / j the signal from the output of the key 42 is fed to one of the inputs of the element OR 53, at the output of which a signal appears about a short circuit in phase F. In the case of a two-phase short circuit: the signal from the output of the key 42 goes to the inputs elements OR 52 and 54, at the outputs of which a short circuit signal appears in phases F. and F. ,. Short circuit signals from the OR elements 52-54 are fed to the registering device 56 and through the OR element 55 to the control system for all phases. For example, the signal is fed to the input of the relay 57 time of the first phase ,. and from its output to one of the inputs of the unit 61 of the comparison. The signal from the output of the latter through the power amplifier 62

and an actuator 63 of the comparator unit, the second input of which

is the rise of the electrode 64. The other input of the comparator unit 61 receives a signal from the actuator 63, and the third input of this comparison unit 61 is a signal from the current sensor 1 through the power setting device 6 and the effective value unit 59. The fourth input of the comparator block 61 receives a signal from the voltage sensor 2 through the block 58

50

connected to the output of the power setting unit, the third input to the time relay output, the fourth input to the output of the actuator, and the output through the power amplifier to the input of the actuator, characterized in that, with a circuit

increase the reliability of the furnace by increasing the accuracy of fixation of effective values. For the case of the full stop of the electrode in the charge, the short circuit of the constant additionally contains four elements, there are no elements in arcing currents, OR there is no registering device, and there is no Also, in each phase of the furnace, the appearance of an asymmetrical system is a constant-current sensor.

Note: there are no higher harmonic components in the arc currents and, therefore, with their zero values in three phases, which are controlled.

the presence of a complete short circuit in an electric arc furnace. Thus, only in the case of a three-phase short circuit, at the output of the logic element AND 39 does a signal appear that goes to one of the inputs of all three, logical elements OR 52-54.

The regulator allows you to quickly respond to the collapse of the charge by raising

ki electrodes with their emphasis in charge. This ensures a reduction in the cost of operation of electric arc furnaces and a reduction in the downtime as a result of accidents. In addition, by reducing the number of false alarms of the automatic regulator to the electrode Lod, as soon as the fact of short circuits is established, the melting time is reduced.

Claims (1)

Invention Formula An automatic power regulator for an electric steel-smelting furnace for smelting metallized pellets, containing in each phase of the furnace a block for effective current value, the input of which is connected to the current sensor output, and an output for input of the power setting block, effective voltage value selection unit, the input of which is connected with the output of the voltage sensor, and the output with the first input connected to the output of the power setting unit, the third input to the time relay output, the fourth input to the output of the actuator, and the output through the power amplifier to the input of the actuator, characterized in that, with a circuit current harmonic sensor, two amplifiers, two adders, three zero-organs, phase element I, two switches, two diodes, two inverters, the output of the constant-current sensor is connected to the inputs of the first and second amplifiers, with the first inputs of the first and second adders with the anode of the first and the cathode of the second diode of this phase, the output of the first amplifier of this phase through the first inverter is connected to the second input of the first advanced phase adder, the output of the second amplifier of this phase through the second inverter is connected to the second input second the adder of the lagging phase, the output of the first adder of this phase through the first null-organ is connected to the first input of the phase element I, the output of the second through the second null-organ to the second input of the phase element I, the output of which is connected to the inputs of the first and second keys of this phase The first key input is connected to the cathode of the first diode, and the second key control input is connected to the second diode of this phase, the output of the first key of the first phase is connected to the first inputs of the first and second elements OR, the output of the second key of the first phase one with a first input The third element OR, the output of the first key of the second phase is connected to the second input of the first and second inputs of the third OR element, the output of the second key of the second phase is connected to the second input of the second OR element, the output of the first key of the third phase is connected to the third inputs of the second and third OR elements, the second key of the third phase is connected to the third input of the first element OR, the fourth. the inputs of the first, second and third OR elements are connected to the output of an AND element, each of the three inputs of which is connected to the output of the harmonic composition sensor of this phase through the third null-organ of this phase, the output of the first OR element is connected to the first inputs of the recording device and the fourth OR element, the output of the JBTO element OR is connected to the second inputs of the registering device and the fourth element OR, the output of the third element OR is connected to the third inputs of the recording device and the fourth element OR, the first code which is connected to the input of the time relay of the first phase, the second output to the input of the time relay of the second phase, and the third output to the input of the time relay of the third phase. shiani four" } w-