JP2018199154A - Speed control system for rolling mill motor - Google Patents

Abstract

To materialize a stable speed control by reducing an actual speed achievement deviation with respect to the speed reference of an AC motor upon tailing off of a material to be rolled.SOLUTION: An inverter device 8 comprises: a speed control part 20 which calculates a torque reference causing the actual speed of an AC motor 3 to match with a speed reference; an armature current control part 21 which calculate the current reference of the armature (thereafter, described as an armature current reference) of the AC motor 3 on the basis of the torque reference; a tailing-off detection part 22 detecting tailing off in which the tail end of a material to be rolled 6 comes off from a work roll 2, on the basis of a fluctuation of rolling load signals; and an armature current compensation circuit part 23 which outputs a negative armature current compensation value for a constant time after the detection of the tailing off. The inverter device 8 supplies AC power to the armature winding 3a of the AC motor 3 on the basis of the armature current reference after compensation in which the negative armature current compensation value is added to the armature current reference.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a speed control system for a rolling mill electric motor.

  A rolling mill disposed in a steel rolling plant includes a work roll for rolling a material to be rolled. The work roll is driven by an AC motor whose speed is controlled by an inverter device. When the tip of the material to be rolled bites into the work roll, an impact load is generated, and there is a problem that the actual speed of the AC motor is temporarily greatly reduced with respect to the speed reference.

  In response to this problem, Patent Document 1 discloses that a predetermined speed increase amount is added to the speed reference when the AC motor is in a no-load state. Thereby, the speed reduction at the time of impact load generation can be reduced.

JP 2009-153314 A

  On the other hand, when the tail end of the material to be rolled comes out of the work roll (so-called tail end slipping, bottom slipping), the load decreases sharply, and there is a problem that the speed performance greatly increases with respect to the speed reference of the AC motor. With the technique of Patent Document 1, the speed fluctuation at the time of biting of the material to be rolled can be reduced, but the speed fluctuation at the time of tail end slipping cannot be reduced.

  The present invention has been made in order to solve the above-described problems, and can reduce the deviation of the actual speed with respect to the speed reference of the AC motor when the material to be rolled comes out of the tail end, and can perform stable speed control. An object of the present invention is to provide a speed control system for a motor for a machine.

  A speed control system for a rolling mill electric motor according to an embodiment of the present invention includes a load cell that outputs a rolling load signal corresponding to a load (rolling load) that a work roll that rolls the material to be rolled receives from the material to be rolled, and a work roll And an inverter device that converts the direct current into alternating current to control the alternating current motor at a variable speed.

  The inverter device includes a speed control unit, an armature current control unit, a tail end missing detection unit, and an armature current compensation circuit unit. The speed control unit calculates a torque reference for matching the actual speed (actual speed) of the AC motor with the speed reference. The armature current control unit calculates a current reference (armature current reference) of the armature of the AC motor based on the torque reference. The tail end drop detection unit detects a tail end drop where the tail end of the material to be rolled comes off the work roll based on the fluctuation of the rolling load signal. The armature current compensation circuit unit outputs a negative armature current compensation value for a predetermined time from when the tail end omission is detected. Then, the inverter device supplies AC power to the armature winding of the AC motor based on the compensated armature current reference obtained by adding the negative armature current compensation value to the armature current reference. Preferably, the negative armature current compensation value is set so as to approach 0 with the passage of time from the detection of the tail end omission.

  Since the load sharply decreases at the timing of the tail end slipping out of the work roll from the work roll, the rolling load signal output from the load cell changes from a predetermined value indicating the rolling state to 0 indicating the rolling end state. The tail end drop detection unit detects the tail end drop from the sudden fluctuation of the rolling load signal. Since the armature current reference is corrected with a negative armature current compensation value for a certain period of time from the detection of the tail end omission, when the load suddenly decreases due to the tail end omission of the rolled material, the deviation of the actual speed from the AC motor speed reference is reduced. Can be reduced. Therefore, a rapid speed increase of the AC motor is suppressed, and stable speed control can be realized.

  Preferably, the AC motor is a synchronous motor, and the inverter device further includes a field current control unit and a field current compensation circuit unit. The field current control unit calculates a field current reference (field current reference) of the synchronous motor based on the magnetic flux reference. The field current compensation circuit unit outputs a negative field current compensation value for a predetermined time from the detection of the tail end omission. Then, the inverter device supplies a direct current to the field winding of the synchronous motor based on the compensated field current reference obtained by adding the negative field current compensation value to the field current reference. Preferably, the negative field current compensation value is set so as to approach 0 as time elapses from the time of detection of the trailing edge missing.

  Since the armature current reference is corrected with the negative armature current compensation value for a certain period of time from the detection of the trailing edge omission, the field current reference is also corrected with the negative field current compensation value. When the load is suddenly reduced due to the trailing edge missing, the deviation of the actual speed with respect to the speed reference of the synchronous motor can be reduced. Therefore, a rapid speed increase of the synchronous motor is suppressed, and stable speed control can be realized.

  More preferably, the tail end missing detection unit detects the tail end missing when the actual speed of the AC motor exceeds a set value with respect to the speed reference.

  Even in a situation where the rolling load signal of the load cell cannot be normally received, it is possible to detect the tail end omission from the upswing of the actual speed with respect to the speed reference. It should be noted that the detection speed of the tail end omission is faster when the tail end omission is detected from the rapid fluctuation of the rolling load signal described above.

  According to the speed control system for a rolling mill electric motor according to an embodiment of the present invention, the deviation of the actual speed with respect to the speed reference of the AC electric motor can be reduced and the stable speed control can be realized when the material to be rolled comes out.

It is a block diagram of the system which concerns on Embodiment 1 of this invention. It is a figure which shows the speed reference | standard at the time of the tail end omission of a to-be-rolled material, and a speed performance. It is a block diagram of the inverter control circuit which concerns on Embodiment 1 of this invention. It is a figure which shows the specific example of the negative armature current compensation value at the time of the tail end omission concerning Embodiment 1 of this invention. It is a figure for demonstrating the presence or absence of compensation of the armature current reference | standard at the time of the tail end omission concerning Embodiment 1 of this invention. It is a flowchart for demonstrating the flow of a process of the inverter control circuit which concerns on Embodiment 1 of this invention. It is a block diagram of the inverter apparatus and field control part which concern on Embodiment 2 of this invention. It is a figure which shows the specific example of the negative field current compensation value at the time of the tail end omission concerning Embodiment 2 of this invention. It is a figure for demonstrating the presence or absence of compensation of the armature current reference | standard at the time of the tail end omission and field current reference | standard concerning Embodiment 2 of this invention. It is a flowchart for demonstrating the flow of a process of the inverter control circuit which concerns on Embodiment 2 of this invention. It is a figure for demonstrating the detection of the tail end omission of the to-be-rolled material which concerns on Embodiment 3 of this invention. It is a conceptual diagram which shows the hardware structural example of the processing circuit (inverter control circuit) which the inverter apparatus 8 mentioned above has.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

Embodiment 1 FIG.
[System Configuration of Embodiment 1]
Embodiment 1 of the present invention will be described with reference to FIGS.

  FIG. 1 is a configuration diagram of a system according to Embodiment 1 of the present invention. The system shown in FIG. 1 is a speed control system for a rolling mill electric motor applied to a steel rolling plant.

  A rolling mill 1 shown in FIG. 1 includes a work roll 2, an AC motor 3, a speed sensor 4, and a load cell 5.

  The work roll 2 is composed of a pair of rolls, and rolls the material 6 to be rolled according to the roll gap. The material 6 to be rolled is a metal material and is conveyed from the left side to the right side in FIG. Further, the rotating shaft of the work roll 2 is connected to the rotating shaft of the AC motor 3.

  The AC motor 3 is driven by three-phase AC to rotate the work roll 2. As an example, the AC motor 3 is a synchronous motor. The armature is arranged as a stator coil (armature winding) on the fixed side, and the field is arranged as a rotor coil (field winding) on the rotating side. The armature may be a rotor and the field may be a stator. In the present embodiment, the AC motor 3 may be an induction motor. Moreover, not only a three-phase alternating current but a single-phase alternating current and a multiphase alternating current may be sufficient.

  The speed sensor 4 is disposed in the vicinity of the rotation shaft of the AC motor 3 and outputs a speed feedback signal corresponding to the rotation speed (speed record) of the AC motor 3.

  The load cell 5 is provided in the vicinity of the work roll 2 and outputs a rolling load signal corresponding to a load that the work roll 2 receives from the material 6 to be rolled (hereinafter referred to as a rolling load).

  The programmable logic controller (hereinafter referred to as PLC) 7 outputs the rolling load signal received from the load cell 5 and the speed reference of the AC motor 3 according to the rolling conditions of the material 6 to be rolled for each control cycle.

  The inverter device 8 converts the direct current into alternating current to control the alternating current motor 3 at a variable speed. The inverter device 8 receives a rolling load signal, a speed reference, a speed feedback signal, etc. for each control period, and supplies power to the AC motor 3 so that the actual speed (actual speed record) of the AC motor 3 matches the speed reference. Supply.

  FIG. 2 is a diagram showing a speed reference and speed results when the material to be rolled 6 is out of the tail end. A broken line 10 indicates the speed reference SP_R. A solid line 11 indicates the speed record SP_F. Time t0 indicates when the rolled material 6 comes out of the work roll 2 and the tail end comes off.

  When the material 6 to be rolled comes out of the work roll 2 at time t0, the load torque is suddenly reduced, so that the actual speed SP_F increases with respect to the speed reference SP_R of the AC motor 3. If a predetermined time elapses due to the speed feedback control, the deviation between the speed reference SP_R and the actual speed SP_F disappears. However, it is desirable that the actual speed SP_F follows the speed reference SP_R at an earlier stage in terms of stability of speed control.

(Block diagram of inverter device 8)
In order to solve such a problem, the inverter device 8 according to the present embodiment is configured as shown in FIG. FIG. 3 is a block diagram for explaining the function of the inverter device 8 according to the first embodiment of the present invention. The inverter device 8 includes an inverter that converts the direct current into alternating current to drive the alternating current motor 3, and an inverter control circuit that controls the output of the inverter. The main circuit of the inverter control circuit includes a speed control unit 20, an armature current control unit 21, a tail end missing detection unit 22, an armature current compensation circuit unit 23, an armature voltage control unit 24, and a PWM controller 25. The voltage type inverter element 26 is a switching element constituting an inverter.

  The speed control unit 20 calculates a torque reference for making the actual speed (speed result) of the AC motor 3 coincide with the speed reference. Specifically, the speed control unit 20 inputs a difference between the speed reference and the speed feedback signal detected by the speed sensor 4 from the outside (PLC 7), and calculates a torque reference for making the difference zero.

  The armature current control unit 21 calculates an armature current reference (hereinafter referred to as an armature current reference) of the AC motor 3 based on the torque reference.

  The inverter device 8 according to the present embodiment includes a tail end missing detection unit 22 and an armature current compensation circuit unit 23 that monitor the rolling state as main features.

  The tail end missing detection unit 22 detects a tail end missing that the tail end of the material 6 to be rolled comes out of the work roll 2 based on the fluctuation of the rolling load signal. Since the load sharply decreases at the timing of the tail end dropout, the rolling load signal output from the load cell 5 changes from a predetermined value indicating the state during rolling to 0 indicating the rolling end state. The tail end drop detection unit 22 detects the tail end drop from the sudden fluctuation of the rolling load signal.

  The armature current compensation circuit unit 23 outputs a negative armature current compensation value for a certain time from the detection of the tail end omission. Preferably, the negative armature current compensation value is set so as to approach 0 with the passage of time from the detection of the tail end omission.

FIG. 4 is a diagram showing a specific example of the negative armature current compensation value when the tail end is lost according to the first embodiment of the present invention. The armature current compensation circuit unit 23 outputs a negative armature current compensation value for a fixed time (compensation section) from the time t0 when the tail end is lost. The negative armature current compensation value is the maximum when the tail end is lost (time t0), decreases with the passage of time, and becomes 0 after the passage of a fixed time (time t1).
The fixed time (compensation interval) can be set arbitrarily.

  The armature current reference output by the armature current control unit 21 is corrected (reduced) by the negative armature current compensation value output by the armature current compensation circuit unit 23 for a certain period of time from the detection of the trailing edge missing. A compensated armature current reference obtained by adding a negative armature current compensation value to the armature current reference is input to the armature voltage control unit 24.

  The armature voltage control unit 24 calculates an armature voltage reference (hereinafter referred to as an armature voltage reference) of the AC motor 3 based on the compensated armature current reference.

  The PWM controller 25 creates a gate pulse by PWM control based on the armature voltage reference. The voltage type inverter element 26 which is a switching element is ON / OFF controlled by a gate pulse, and the inverter device 8 supplies AC power to the armature winding 3 a of the AC motor 3.

  FIG. 5 is a diagram for explaining whether or not the armature current reference is compensated when the tail end is disconnected according to the first embodiment of the present invention. The solid line 40 represents the armature current reference when there is no compensation, and the broken line 41 represents the armature current reference when there is compensation. By correcting the armature current reference with the negative armature current compensation value shown in FIG. 4 at each time in the compensation section, fluctuations in the current reference after the tail end can be suppressed as shown by the broken line 41. . As a result, the speed fluctuation of the AC motor 3 can be suppressed.

(Processing flow of inverter control circuit)
FIG. 6 is a flowchart for explaining a process flow of the inverter control circuit according to the first embodiment of the present invention. The routine shown in FIG. 6 is repeatedly executed every control cycle. At the first execution, the value of t is set to n (n: indicates the end of the compensation interval). At the second and subsequent executions, the value of t in the previous routine is taken over.

  First, in step S <b> 100, the inverter control circuit inputs a speed reference and a rolling load signal in the current control cycle from the PLC 7, and inputs a speed feedback signal from the speed sensor 4.

  Next, in step S105, the speed control unit 20 calculates a torque reference for setting the difference between the speed reference and the speed feedback signal to zero.

  Next, in step S110, the armature current control unit 21 calculates an armature current reference based on the torque reference.

  Moreover, in step S115, the tail end missing part detection part 22 determines whether it is at the time of tail end missing generation based on the fluctuation | variation of a rolling load signal. If it is the timing at which the tail end omission is detected, the process proceeds to step S120. In other cases, that is, when rolling or after the end of rolling (at the end of the tail end), The process proceeds to step S145.

  If it is the timing when the tail end omission is detected, a time counter t indicating the elapsed time after the tail end omission is initialized with 0 in step S120.

  In step S <b> 125, the armature current compensation circuit unit 23 outputs a negative armature current compensation value for a predetermined time from the detection of the tail end omission. Specifically, as shown in FIG. 4, a negative armature current compensation value corresponding to the value of the time counter t is output.

  In step S130, the compensated armature current reference is calculated by adding the negative armature current compensation value calculated in step S125 to the armature current reference calculated in step S110. In step S135, the armature voltage control unit 24 calculates the armature voltage reference based on the compensated armature current reference. In step S140, the voltage type inverter element 26 is controlled by the gate pulse corresponding to the armature voltage reference.

  Thereafter, the value of the time counter t is taken over, and this routine is executed in the next control cycle. In the next control cycle, since the tail end omission has already occurred, the determination condition in step S115 is not satisfied, and the process proceeds to step S145.

  In step S145, the tail end drop detection unit 22 determines whether or not the value of the time counter t has reached n. Until the value of the time counter t reaches n, the process proceeds to step S150. In step S150, the time counter t is incremented, and in the processing after step S150, the armature current reference is corrected with the negative armature current compensation value based on the new time counter t. On the other hand, if the value of the time counter t has reached n in step S145, the armature current reference correction ends because a certain time (compensation section) has elapsed since the detection of the tail end omission.

  As described above, according to the routine shown in FIG. 6, when the load suddenly decreases due to the trailing end of the material to be rolled 6, the deviation of the actual speed with respect to the speed reference of the AC motor 3 can be reduced, and stable speed control can be realized. .

  By the way, although the voltage type inverter is used in the inverter device 8 of the first embodiment described above, the present invention can also be applied to a current type inverter. This point is the same in the following embodiments.

(Hardware configuration example of inverter control circuit)
FIG. 12 is a conceptual diagram illustrating a hardware configuration example of a processing circuit (inverter control circuit) included in the inverter device 8 described above. Each part in FIG. 3 (and FIG. 7 described later) represents a part of the function, and each function is realized by a processing circuit. As one aspect, the processing circuit includes at least one processor 91 and at least one memory 92. In another aspect, the processing circuit comprises at least one dedicated hardware 93.

  When the processing circuit includes the processor 91 and the memory 92, each function is realized by software, firmware, or a combination of software and firmware. At least one of software and firmware is described as a program. At least one of software and firmware is stored in the memory 92. The processor 91 implements each function by reading and executing the program stored in the memory 92.

  When the processing circuit includes dedicated hardware 93, the processing circuit is, for example, a single circuit, a composite circuit, a programmed processor, or a combination thereof. Each function is realized by a processing circuit.

Embodiment 2. FIG.
[System Configuration of Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIGS. The system of this embodiment can be realized by causing the inverter control circuit to execute the routine of FIG. 6 and FIG. Hereinafter, a description will be given focusing on differences from the first embodiment. In the second embodiment, the AC motor 3 is a synchronous motor.

(Block diagram of inverter device 8)
FIG. 7 is a block diagram for explaining the function of the inverter device 8 according to the second embodiment of the present invention. In the second embodiment, the inverter control circuit includes a field circuit in addition to the main circuit of FIG. 3 described above. The field circuit includes a field current control unit 27, a field current compensation circuit unit 28, a field voltage control unit 29, and a phase controller 30. The thyristor element 31 is a switching element that constitutes a rectifier for supplying a direct current to the field winding 3b.

  The field current control unit 27 calculates a field current reference (hereinafter referred to as a field current reference) of the AC motor 3 based on the magnetic flux reference. The tail end missing detection unit 22 described above is connected to the field current compensation circuit unit 28 in addition to the armature current compensation circuit unit 23, and a signal at the time of tail end missing detection is transmitted to both.

  The field current compensation circuit unit 28 outputs a negative field current compensation value for a predetermined time from when the tail end omission is detected. Preferably, the negative field current compensation value is set so as to approach 0 as time elapses from the time of detection of the trailing edge missing.

  FIG. 8 is a diagram showing a specific example of the negative field current compensation value when the tail end is lost according to the first embodiment of the present invention. The field current compensation circuit unit 28 outputs a negative field current compensation value for a fixed time (compensation period) from the time t0 when the tail end is lost. The negative field current compensation value is maximum when the tail end is lost (time t0), decreases with time, and becomes 0 after a certain time (time t1). The fixed time (compensation section) is the same as the compensation section in FIG. The field current compensation value shown in FIG. 8 is different from the armature current compensation value shown in FIG.

  The field current reference output by the field current control unit 27 is corrected (reduced) with the negative field current compensation value output by the field current compensation circuit unit 28 for a certain period of time from the detection of the tail end omission. A field current reference after compensation obtained by adding a negative field current compensation value to the field current reference is input to the field voltage control unit 29.

  The field voltage control unit 29 calculates a field voltage reference (hereinafter referred to as a field voltage reference) of the AC motor 3 based on the compensated field current reference.

  The phase controller 30 creates a gate pulse by phase control based on the field voltage reference. The thyristor element 31 is ON / OFF controlled by a gate pulse, and the inverter device 8 supplies a direct current to the field winding 3 b of the AC motor 3.

  FIG. 9 is a diagram for explaining whether or not the armature current reference and the field current reference are compensated when the tail end is disconnected according to the second embodiment of the present invention. The solid line 40 represents the armature current reference without compensation, and the broken line 41 represents the armature current reference with compensation, which is the same as FIG. The solid line 42 represents the field current reference without compensation, and the broken line 43 represents the field current reference with compensation. By correcting the field current reference with the negative field current compensation value shown in FIG. 8 at each time in the compensation section, the fluctuation of the current reference after the tail end can be suppressed as shown by the broken line 43. . As a result, the speed fluctuation of the AC motor 3 can be suppressed.

(Processing flow of inverter control circuit)
In the second embodiment, the inverter control circuit executes the field control routine shown in FIG. 10 simultaneously with the armature control routine shown in FIG. The routine shown in FIG. 10 is repeatedly executed every control cycle. At the first execution, the value of t is set to n (n: indicates the end of the compensation interval). At the second and subsequent executions, the value of t in the previous routine is taken over.

  First, in step S200, the inverter control circuit inputs a magnetic flux reference and a rolling load signal in the current control cycle.

  In step S205, the field current control unit 27 calculates a field current reference based on the magnetic flux reference.

  Moreover, in step S210, the tail end missing part detection part 22 determines whether it is at the time of tail end missing generation based on the fluctuation | variation of a rolling load signal. If it is the timing at which the tail end omission is detected, the process proceeds to step S215. In other cases, that is, when rolling or after the end of rolling (at the end of the tail end), The process proceeds to step S240.

  If it is the timing when the tail end omission is detected, a time counter t indicating the elapsed time after the tail end omission is initialized with 0 in step S215.

  In step S220, the field current compensation circuit unit 28 outputs a negative field current compensation value for a predetermined time from the detection of the tail end omission. Specifically, as shown in FIG. 8, a negative field current compensation value corresponding to the value of the time counter t is output.

  In step S225, the compensated field current reference is calculated by adding the negative field current compensation value calculated in step S220 to the field current reference calculated in step S205. In step S230, the field voltage control unit 29 calculates a field voltage reference based on the compensated field current reference. In step S235, the thyristor element 31 is controlled by a gate pulse corresponding to the field voltage reference.

  Thereafter, the value of the time counter t is taken over, and this routine is executed in the next control cycle. In the next control cycle, since the tail end omission has already occurred, the determination condition of step S210 is not satisfied, and the process proceeds to step S240.

  In step S240, the tail end drop detection unit 22 determines whether or not the value of the time counter t has reached n. The process proceeds to step S245 until the value of the time counter t reaches n. In step S245, the time counter t is incremented, and in the processing after step S245, the field current reference is corrected with the negative field current compensation value based on the new time counter t. On the other hand, when the value of the time counter t has reached n in step S240, since a certain time (compensation section) has elapsed since the detection of the tail end omission, the field current reference correction ends.

  As described above, according to the routine shown in FIG. 10, the armature current reference is corrected with the negative armature current compensation value by the routine of FIG. Since the current reference is also corrected with the negative field current compensation value, the deviation of the speed record with respect to the speed reference of the synchronous motor can be reduced when the load suddenly decreases due to the trailing edge of the material 6 to be rolled. Therefore, a rapid speed increase of the synchronous motor is suppressed, and stable speed control can be realized.

Embodiment 3 FIG.
[System Configuration of Embodiment 3]
Next, Embodiment 3 of the present invention will be described with reference to FIG. The system of the present embodiment is realized by adding a process described later to the tail end missing detection unit 22 in the first or second embodiment. Hereinafter, a description will be given focusing on differences from the second embodiment.

  As described in the first embodiment, it is desirable from the viewpoint of detection speed that the tail end omission of the material 6 to be rolled is detected from the fluctuation of the rolling load signal of the load cell. However, there may be a situation where the rolling load signal of the load cell cannot be received normally. Therefore, the tail end missing detection unit 22 according to the present embodiment adds a process of detecting tail end missing when the actual speed (actual speed) of the AC motor 3 exceeds the set value with respect to the speed reference. did.

  As shown in FIG. 11, even if there is no change in the speed reference, the fact that the speed based on the speed feedback signal output from the speed sensor 4 has risen above a certain level can detect a tail end slippage due to the end of rolling. When the tail end omission is detected, correction to reduce the armature current reference and the field current reference is performed as in the first and second embodiments.

  According to the tail end missing detection unit 22 according to the third embodiment, it is possible to detect the tail end missing from the actual speed overshoot with respect to the speed reference. Therefore, even in a situation where the rolling load signal of the load cell cannot be normally received, the deviation of the speed record with respect to the speed reference of the AC motor can be reduced, and stable speed control can be realized.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Rolling machine 2 Work roll 3 AC motor 3a Armature winding 3b Field winding 4 Speed sensor 5 Load cell 6 Rolled material 7 PLC
DESCRIPTION OF SYMBOLS 8 Inverter apparatus 20 Speed control part 21 Armature current control part 22 Tail end omission detection part 23 Armature current compensation circuit part 24 Armature voltage control part 25 PWM controller 26 Voltage type inverter element 27 Field current control part 28 Field magnet Current compensation circuit unit 29 Field voltage control unit 30 Phase controller 31 Thyristor element

Claims (5)

A load cell that outputs a rolling load signal corresponding to a load that the work roll that rolls the material to be rolled receives from the material to be rolled;
An AC motor for driving the work roll;
Comprising an inverter device for variable speed control of the AC motor by converting DC to AC;
The inverter device is
A speed control unit that calculates a torque reference for matching the actual speed of the AC motor to the speed reference;
An armature current control unit that calculates an armature current reference of the AC motor based on the torque reference (hereinafter referred to as an armature current reference);
A tail end slip detection unit for detecting a tail end slippage in which the tail end of the material to be rolled slips out of the work roll based on a change in the rolling load signal;
An armature current compensation circuit unit that outputs a negative armature current compensation value for a certain period of time from when the tail end omission is detected, and
Supplying AC power to the armature winding of the AC motor based on the armature current reference after compensation obtained by adding the negative armature current compensation value to the armature current reference;
A speed control system for an electric motor for a rolling mill. The negative armature current compensation value approaches 0 with the passage of time from the detection of the tail end omission,
The speed control system of the electric motor for rolling mills according to claim 1. The AC motor is a synchronous motor,
The inverter device is
A field current control unit that calculates a field current reference of the synchronous motor based on a magnetic flux reference (hereinafter referred to as a field current reference);
A field current compensation circuit unit that outputs a negative field current compensation value for a certain period of time from when the tail end omission is detected, and
Supplying a DC current to the field winding of the synchronous motor based on the compensated field current reference obtained by adding the negative field current compensation value to the field current reference;
The speed control system of the electric motor for rolling mills according to claim 1 or 2. The negative field current compensation value approaches 0 with the lapse of time from the detection of the tail end omission,
The speed control system of the motor for rolling mills according to any one of claims 1 to 3. The tail end drop detection unit detects the tail end drop when the actual speed of the AC motor exceeds a set value with respect to the speed reference;
The speed control system of the electric motor for rolling mills according to any one of claims 1 to 4.

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