RU2334926C2 - Position regulator of electrode of electric arc steel smelting furnace - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention refers to electrothermics, particularly to automated position regulators of electrodes of electric arc steel smelting furnaces. According to the invention for each phase of the electric arc furnace the regulator contains a setting power mechanism, a unit of a dead band, an output of which is connected with the input of controlled reverse converter, to the output of which an electric engine of electrode travel is connected, and a threshold component, the output of which is connected to the control input of a controlled switch. The regulator is equipped with a magnifier, with a limit unit, an aperiodic filter, a summator and a unit for separation of error signal module, the output of which is connected to the input of the threshold component, while the input is connected with the output of the setting power mechanism, the first input of the summator and input of the magnifier, the output of which via the limit unit is connected with the input of the control switch, the output of which via the aperiodic filter is connected to the second input of the summator, the output of which is connected with the input of dead band unit.

EFFECT: upgraded efficiency of furnace and reduction of specific consumption of electric power.

3 dwg

Description

The invention relates to electrothermics, in particular to automatic regulators of the position of the electrodes of an arc steelmaking electric furnace.

Known regulator of the position of the electrodes, containing a power adjuster, a dead band unit, a feedback potentiometer, a reversible converter, the output of which is connected to an electrode displacement motor, and a time relay element [1]. However, this regulator does not provide quality control of the power introduced into the electric furnace.

Also known is the position controller of the electrodes of the electric arc furnace, comprising a power adjuster, a dead band unit connected to the input, the output of which is connected to the input of a controlled reversible converter connected to the electrode displacement motor, and a rectifier bridge [2]. The disadvantage of this regulator is the low accuracy of regulation.

The closest in technical essence or prototype is the electrode position regulator, containing for each phase of the electric furnace a power switch, the output of which is connected to the inputs of the first and second threshold elements and the input of the dead band unit, the first output of which is connected to the negative feedback potentiometer slider, covering the controlled reversible a converter, to the output of which an electrode displacement motor is connected, the input of the reversing converter through the first diagonal the bridge bridge is connected to the second input of the deadband unit, and the second diagonal of the bridge bridge is connected to the outputs of the controlled key, the input of which through the OR element is connected respectively to the outputs of the first and second threshold elements [3].

This regulator cannot maintain the specified electrical mode with high accuracy due to the presence of a control error, the value of which is greater, the greater the magnitude of the dead band of the regulator, which in turn is a parameter of its setting, ensuring the stability of the regulatory process. Such a regulator can maintain power for a long time at the lower (for example, when the electrode is continuously lowered during the well penetration) or upper (when the electrode is lifted after the wells are penetrated in the charge and the liquid metal level in the furnace bath is continuously increasing) the dead zone limits. In both cases, it is obvious that the electric mode of the furnace differs from the optimal (predetermined) one and, therefore, the performance of the electric arc furnace (productivity and specific energy consumption) is reduced. In addition, such a regulator does not provide independent adjustment of the accuracy and stability of the regulatory process.

The objective of the invention is to increase the accuracy of maintaining a given electrical mode (with the possibility of independent adjustment of the stability of regulation) by continuously correcting the input signal of the dead band unit with an additional signal as a function of the sign of the error signal within the static dead band.

The specified technical result is achieved by a known position controller of the electrode of the steelmaking electric furnace, containing for each phase of the electric furnace a power adjuster, a dead band unit, the output of which is connected to the input of a controlled reversible converter, the output of which is connected to an electrode displacement motor, and a threshold element, the output of which is connected with a control key input, it is additionally equipped with an amplifier, restriction unit, aperiodic filter, adder and an error signal module isolation unit, the output of which is connected to the input of the threshold element, and the input is connected to the output of the power adjuster, the first input of the adder and the amplifier input, the output of which is connected through the restriction block to the input of the controlled key, the output of which is connected through the aperiodic filter to the second input an adder, the output of which is in turn connected to the input of the deadband unit.

Comparative analysis with the prototype allows us to conclude that the claimed position controller allows, in the presence of a block of a static dead zone in its structure, which ensures the stability of the regulation process, to increase the accuracy of maintaining a given electrical mode and the economic performance of the electric furnace.

Therefore, the claimed technical solution meets the criterion of "Novelty."

Comparison of the proposed solution not only with the prototype, but also with other technical solutions in this technical field did not allow us to identify in them the features that distinguish the claimed solution from the prototype, which allows us to conclude that the criterion of "Inventive step".

The essence of the proposed technical solution is confirmed by the drawing (figure 1), which shows a diagram of the position controller of the electrode of an electric arc steel furnace.

The controller contains a controlled reversible converter 1, the output of which is connected to an electric motor 2 for moving the electrode 3. The input of the controlled reversible converter 1 is connected to the output of the dead band unit 4, the input of which is connected to the output of the adder 5. The first input of the adder 5 is connected to the output of the power generator 6, the input the amplifier 7 and the input of the allocation unit of the module 8 error signal, the output of which through the threshold element 9 is connected to the control input of the managed key 10. The output of the amplifier 7 through the block is limited Iya 11 is connected to the input of the controlled key 10, the output of which through an aperiodic filter 12 is connected to the second input of the adder 5.

The threshold value of the threshold element 9 is selected so that an additional correction signal from the output of the amplifier 7 through the block 11, the controlled key 10 and the aperiodic filter 12 are fed to the second input of the adder 5 within the deadband of block 4. The threshold value of the block 11 is modulo the threshold value of the signal of the static dead zone of block 4, and the sign corresponds to the sign of the signal of the regulation error.

The position controller of the electrode of the arc steel furnace operates as follows.

If there is an error signal at the output of the power setter 6 that exceeds the threshold of the dead zone of block 4, a signal appears at the input and the voltage at the output of the controlled converter 1, while the electric motor 2 moves the electrode 3 in the direction of decreasing, mismatch. At this time, there are signals at the input and output of the amplifier 7, the output of the restriction link 11 and the input of the managed key 10. There are signals also at the input and output of the allocation link of module 8, as well as the input of the threshold element 9. Signals at the output of the threshold element 9, the control input and the output of the managed key 10 is missing. In this case, an additional correction signal from the output of the amplifier 7 through the restriction block 11, the controlled key 10 and the aperiodic filter 12 does not enter the second input of the adder 5.

When the error signal at the output of the power setter 6 decreases to a value close to the threshold signal of the dead zone of block 4, signals appear at the output of the threshold element 9 and the control input of the controlled key 10. In this case, an additional correction signal from the output of the restriction block 11 through the open key 10 and the aperiodic filter 12 enters the second input of the adder 5, smoothly outputting an error signal at the input of block 4 beyond the threshold of the dead band by an amount equal in magnitude to the threshold signal stat cal deadband. In this case, the electric motor 2 continues to move the electrode 3 in the direction of decreasing the mismatch. When the value of the error signal at the output of the power setter 6 reaches zero, the additional correction signal at the output of the amplifier 7 becomes zero, the signals at the second input of the adder 5 disappear, at the output of the dead band unit 4, the input of the controlled converter 1, and also the voltage at its output. The electric motor 2 stops, stopping to move the electrode 3.

If during the braking of the electric motor 2 an error signal of opposite polarity appears at the output of power setter 6 at the output of amplifier 7 and the second input of adder 5, an additional correcting signal of opposite polarity also appears again, which smoothly outputs a new error signal at the input of block 4 beyond the other threshold of the zone threshold deadband by an amount also equal in magnitude to the threshold signal of the static deadband. In this case, signals of opposite polarity appear at the output of the dead band unit 4, the input of the controlled converter 1 and the voltage at its output. The electric motor 2 in this case moves the electrode 3 in the opposite direction until the new mismatch is eliminated to zero.

With a zero value of the error signal at the output of the power setter, the correction signal at the output of amplifier 7 and, respectively, the second input of adder 5 is equal to zero, there are also no signals at the output of the dead band unit 4 and the input of the controlled converter 1, the electric motor 2 for moving the electrode 3 is stationary, the controlled key 10 is open . At the next occurrence of an error signal at the output of the power setter 6 within the deadband at the second input of the adder 5, a correction signal of the corresponding polarity appears again and the motor 2 moves the electrode 3 in the direction of eliminating the mismatch.

In the event that an error signal exceeds the threshold of the deadband of unit 4 at the output of power setter 6, the signals at the output of threshold element 9 and the input of controlled key 10 disappear, key 10 is closed, and the operation of the controller is repeated in the described order.

Thus, the proposed controller, when the regulation error signal is located within the dead band, shifts the static response of the dead band unit (respectively, “left” or “right” depending on the sign of the error signal) by continuously feeding an additional correction signal to its input through the adder. Moreover, the maximum value of the additional signal is equal in absolute value to the threshold value of the dead band unit, and the sign corresponds to the error sign. When eliminating the error of regulation to zero (close to zero), the correction signal is automatically removed, thereby increasing the accuracy of maintaining the specified electric mode of the furnace, its performance and decreasing the specific energy consumption.

To understand the essence of the technical solution proposed by the authors, we give a more detailed description of the processes that occur when regulating the electric mode in an electric arc furnace using known regulators and the proposed one.

In the known solution, over a period of time t ₁ (Fig. 2) of the period of penetration of wells in a solid charge (in the absence of collapses), the arc length is continuously lengthened (due to the swelling of the molten metal on the hearth of the furnace), while the arc current is correspondingly reduced and the controller is constantly working to lower the electrode, maintaining the value of the arc current at the lower boundary of the dead band (i = I _min1 <I _s , Fig. 1). When the charge collapses during this period and the regulator performs a short circuit (for example, at time t ₁₁ ), the furnace electrode can stop in any position within the dead zone 2ΔI ₁ and, accordingly, the arc current can take a value in the range from I _min1 to I _max1 (segment Δt ₁ , figure 2). For i> I _min1 , as the charge melts, the arc current due to the continuous extension of the arc decreases to the value i = I _min1 .

At the end of the penetration of the wells, the level of liquid metal in the furnace bath is constantly growing, and the arc length is constantly decreasing, while the arc current is increasing and the furnace electrodes are constantly rising up under the influence of such regulators. In this case, the arc current is maintained at the level of the upper boundary of the dead zone 2ΔI ₁ (I _max1 > I _s ). When the charge collapses during this period (t ₂ , FIG. 2) and the regulator works out a short circuit (for example, the time interval Δt ₂ ), the arc current can have any value within the dead zone 2ΔI _{1 of} this melting period up to a value equal to I _min1 . As the liquid metal level rises, the arc current again increases to a value equal to I _max1 . A similar picture (different from the optimally defined one) is observed during the melting periods t ₁ and t ₂ after the regulator cuts off the arc break.

After melting the solid charge (metallurgical periods of smelting t ₃ and t ₄ ), the electric mode of the furnace, as you know, becomes calmer and the dead zone of the regulator is usually narrowed by the control system (figure 2). However, the arc current after working out the perturbation during these periods can be maintained for a long time by such a regulator also in the region of the boundaries of the dead zones (I _min2 , I _max2 and I _min3 , I _{max3, respectively} ) and may not correspond to the optimal value.

Thus, in the known controllers within the dead zone (s), the mismatch of the arc current value to the set value by the regulator is not eliminated (since it removes the control action within the dead band) and, therefore, the optimally set mode of the arc furnace is not ensured.

(t<t₁, фиг.3) регулятор также воздействует на механизм перемещения электрода в сторону его опускания, увеличивав ток дуги. При достижении током дуги значения, равного нижнему значению границы зоны нечувствительности

(момент времени t₁ на фиг.3), ее граница плавно сдвигается регулятором в сторону увеличения значения Imin_i на величину ΔIi до значения, равного I_з (зона нечувствительности в целом плавно сдвигается дополнительно введенными элементами на величину, равную порогу чувствительности, фиг.3). При этом регулируемый параметр (ток дуги) оказывается вне сдвигающейся зоны нечувствительности (точка А) и регулятор продолжает опускать электрод, увеличивая ток дуги. При достижении током дуги заданного значения (точка В, момент времени t₂ на фиг.3) регулятор снимает управляющее воздействие, а граница зоны нечувствительности возвращается на исходную позицию (вся зона нечувствительности плавно возвращается в первоначальное положение, момент времени t₃ на фиг.3). При этом ток дуги устанавливается на уровне заданного значения (i=I_з).In the proposed solution, when the arc current of the i-th stage of melting is less

(t <t ₁ , Fig. 3) the controller also acts on the mechanism for moving the electrode in the direction of its lowering, increasing the arc current. When the arc current reaches a value equal to the lower value of the dead band boundary

(time t ₁ in Fig. 3), its boundary is smoothly shifted by the regulator in the direction of increasing the value of Imin _i by ΔIi to a value equal to I _s (the dead zone as a whole is smoothly shifted by additionally introduced elements by an amount equal to the sensitivity threshold, Fig. 3). In this case, the adjustable parameter (arc current) is outside the moving dead zone (point A) and the controller continues to lower the electrode, increasing the arc current. When the arc current reaches the set value (point B, time t ₂ in FIG. 3), the controller removes the control action, and the border of the dead band returns to its original position (the entire dead band smoothly returns to its original position, time t ₃ in FIG. 3 ) In this case, the arc current is set at the set value level (i = I _s ).

(t<t₁*, фиг.3) регулятор воздействует на механизм перемещения электрода в сторону его подъема, уменьшая ток дуги. При достижении током дуги значения, равного верхнему значению границы зоны нечувствительности

(момент времени t₁* на фиг.3), ее граница сдвигается в сторону уменьшения значения

на величину - ΔIi до значения, равного Iз (зона нечувствительности в целом плавно сдвигается дополнительно введенными элементами на величину, равную порогу чувствительности, но с обратным знаком, фиг.3). При этом регулируемый параметр (ток дуги) оказывается вне сдвигающейся зоны нечувствительности (точка А*) и регулятор продолжает поднимать электрод, уменьшая ток дуги. При достижении током дуги заданного значения (точка В*, момент времени t₂* на фиг.3) регулятор снимает управляющее воздействие, а граница зоны нечувствительности возвращается на исходную позицию (вся зона нечувствительности плавно возвращается в первоначальное положение, момент времени t₃*). Таким образом, в предлагаемом техническом решении регулятор воздействует на механизм перемещения электрода в двух случаях: а) при нахождении стабилизируемого параметра (тока дуги) вне установленной зоны нечувствительности за счет наличия сигнала на выходе блока зоны нечувствительности, б) при нахождении стабилизируемого параметра внутри статической зоны нечувствительности, изменением (сдвигом) ее позиции относительно заданного значения регулируемого параметра (одновременным увеличением или уменьшением пороговых значений границ зоны нечувствительности). Изменение позиции зоны нечувствительности приводит к появлению сигнала на выходе блока зоны нечувствительности и формированию регулятором управляющего воздействия на механизм перемещения электрода. Причем в первом случае задачей регулятора является введение регулируемого параметра в границы статической зоны нечувствительности (устойчивость регулирования), а во втором - доведение регулируемого параметра до заданного (оптимального) значения (точность регулирования).When the arc current is greater

(t <t ₁ *, Fig. 3) the regulator acts on the mechanism of electrode movement in the direction of its rise, reducing the arc current. When the arc current reaches a value equal to the upper value of the dead band boundary

(time t ₁ * in Fig. 3), its boundary shifts toward a decreasing value

by a value of ΔIi to a value equal to Iз (the dead zone as a whole is smoothly shifted by additionally introduced elements by an amount equal to the sensitivity threshold, but with the opposite sign, Fig. 3). In this case, the adjustable parameter (arc current) is outside the moving dead zone (point A *) and the controller continues to raise the electrode, decreasing the arc current. When the arc current reaches the set value (point B *, time t ₂ * in Fig. 3), the controller removes the control action, and the border of the dead zone returns to its original position (the entire dead zone smoothly returns to its original position, time t ₃ *) . Thus, in the proposed technical solution, the regulator acts on the mechanism of electrode movement in two cases: a) when the stabilized parameter (arc current) is outside the set dead band due to the presence of a signal at the output of the dead band block, b) when the stabilized parameter is inside the static zone insensitivity, by changing (shifting) its position relative to a given value of an adjustable parameter (by simultaneously increasing or decreasing threshold values of s insensitivity). A change in the position of the dead band leads to the appearance of a signal at the output of the dead band unit and the formation by the regulator of a control action on the electrode movement mechanism. Moreover, in the first case, the regulator's task is to introduce an adjustable parameter into the boundaries of the static deadband (regulation stability), and in the second, to bring the adjustable parameter to a predetermined (optimal) value (regulation accuracy).

Additionally, we note that in the proposed solution, increasing the accuracy of regulation of the electric mode of the furnace is not achieved by reducing the value of the static dead zone (the limits of its reduction for each of the melting periods are limited and are associated with a significant deterioration in the quality of the regulation process, and most importantly, with a loss of stability), and by maintaining its value at the lowest possible level for a given melting period, ensuring the stability of the regulation process, and additionally changing its position (preserving the values of optimally selected thresholds of sensitivity) relative to a given value when the adjustable parameter is within the established static deadband.

Information sources

1. USSR author's certificate No. 698174, cl. HB05 7/148, 1979.

2. Copyright certificate of the USSR No. 701513, class. HB05 7/148, 1979,

3. USSR copyright certificate No. 1424702, cl. HB05 7/148, 1987.

Claims (1)

The electrode position regulator of the arc steelmaking electric furnace, comprising for each phase of the electric furnace a power adjuster, a dead band unit, the output of which is connected to the input of the controlled reversible converter, the output of which is connected to the electrode moving motor, and a threshold element, the output of which is connected to the control input of the controlled key, different the fact that it is additionally equipped with an amplifier, a restriction unit, an aperiodic filter, an adder, and a signal module allocation unit faults, the output of which is connected to the input of the threshold element, and the input is connected to the output of the power setter, the first input of the adder and the input of the amplifier, the output of which is connected through the restriction block to the input of the controlled key, the output of which is connected through the aperiodic filter to the second input of the adder, the output of which with the input of the deadband unit.

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