JPH0478363B2 - - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a rolling mill that controls the speed of an electric motor that drives the rolling mill at a predetermined acceleration/deceleration according to a rolling schedule so as to match a speed standard. The present invention relates to a control device for a drive motor.

(Prior Art) Conventionally, in a single stand rolling mill, the rolling speed has been set in advance by the operator before rolling starts, based on the capacity of the drive motor and the rolling schedule.
During rolling, operators monitored the current flowing through the motor each time they adjusted the rolling reduction or tension, and if the current was excessive, they would reduce the rolling speed, or increase the rolling speed if necessary.

FIG. 2 is a block diagram of the portion forming the speed reference for the drive motor of such a conventional device. It is equipped with a rolling speed setter 20 for the operator to set the rolling speed, and a low speed setter 21 for setting a lower rolling speed, and is connected to a function generator via an acceleration command contact 23 or a deceleration command contact 24, respectively. Guided by 22. Function generator 22
When the speed command signal from the setter 20 or 21 is input, it outputs a speed reference with a ramp function corresponding to a predetermined acceleration or deceleration. A speed control device (not shown) controls the speed of the drive motor in accordance with this speed reference. When the operator sets the rolling speed using the rolling speed setter 20 according to the rolling schedule and generates a speed reference via the acceleration command contact 23 and the function generator 22, the set rolling will continue as is unless the operator intervenes in the middle. accelerate to speed. When the acceleration is completed and the set rolling speed is reached, the constant speed holding command contact 25 provided between the input and output terminals of the function generator 22 is turned on, and the acceleration command contact 23 is turned off. Similarly, when decelerating, the deceleration command contact 24 is selectively turned on, and the function generator 22 generates a speed reference for decelerating to a low speed. When stopping a driving electric motor, a stop command, that is, a zero speed command is given to the function generator 22 via the stop command contact 26, thereby generating a speed standard that causes the motor to stop with a predetermined deceleration. Ru.

(Problems to be Solved by the Invention) In conventional equipment, speed control is mainly focused on the rolling speed according to the rolling schedule, and if an excessive current is found to be flowing through operator monitoring, rolling is stopped. This was addressed by lowering the speed settings. but,
When changing the speed, a decelerating current or an accelerating current flows for a short period of time until the speed becomes stable, so it is not always easy to set the rolling speed to an appropriate rolling speed at which an appropriate rolling current can be obtained. If the rolling speed is reduced more than necessary, the operating efficiency will be lowered, and conversely, if the rolling speed is too high, in the worst case, the protection device may be activated due to overload, leading to interruption of operation. be.

Therefore, the present invention provides a rolling mill drive system that automatically controls the rolling speed according to the capacity of the drive motor, eliminating the need for operator-dependent operations such as setting the rolling speed and adjusting the rolling speed during operation. The object of the present invention is to provide a control device for an electric motor.

[Structure of the invention]

(Means for Solving the Problems) A control device for a rolling mill driving electric motor according to the present invention includes a current detecting means for detecting a current of the motor, and an acceleration/deceleration of the motor based on the current detected by the current detecting means. a calculation means for calculating a rolling current component by subtracting an acceleration/deceleration current component required for the rolling current component; a target rolling current component setting means for setting a target value for the rolling current component;
Comparing means for comparing the rolling current component and the target value and outputting a comparative output signal according to the magnitude relationship between the two, and a rolling state signal and a comparative output signal indicating whether the rolling mill is accelerating, decelerating or at constant speed. A logical means that makes a logical judgment according to a combination of the following and outputs an acceleration command, a constant speed hold command, or a deceleration command; The present invention is characterized in that it includes speed reference setting means for setting a speed reference for the control system.

(Function) Roughly speaking, the current flowing through the motor can be considered to consist of an acceleration/deceleration current component that occurs transiently due to acceleration/deceleration, and a rolling current component that is always necessary. The more the latter rolling current component is below the rated current value of the drive motor and closer to the rated value, the more efficiently the capacity of the drive motor is utilized. This is because the acceleration/deceleration time of a rolling mill is relatively short, and especially in the case of a single-stand rolling mill, the frequency of acceleration/deceleration is relatively infrequent.
This is because even if an accelerating current flows, it can often be sufficiently covered by the short-term overload capability of the motor. Therefore, according to the present invention, attention is paid to the rolling current component remaining after the acceleration/deceleration current component is subtracted, and the speed reference is automatically corrected so that this rolling current component approaches a predetermined value, for example, a rated current value. Therefore, according to the present invention, the capacity of the electric motor can be fully utilized to maximize the operating efficiency without interrupting the operation due to the activation of the overload protection device based on acceleration or reducing the operating efficiency due to low speed. can be improved.

(Example) FIG. 1 shows an example of the present invention.
The rolling roll 1 is driven by an electric motor 2. The electric motor 2 is driven at variable speed by an adjustable power converter 3. The electric motor 2 is controlled via a speed controller 5 and a power converter 3 controlled by the speed controller 5 so that the rolling speed detected by the speed detector 4 matches the speed reference output from the function generator 22. Speed controlled.

A motor current I _n is detected by a current detector 6, and its detection signal is led to a calculator 7. on the other hand,
An acceleration/deceleration current I _a of the electric motor 2 is given from an acceleration/deceleration current calculator 8 . There are various ways to obtain the acceleration/deceleration current I _a , but for example, it can be stored as a function of acceleration/deceleration and speed based on the results of measurements made in advance, and the required acceleration/deceleration current can be calculated based on the acceleration and speed each time. Alternatively, it may be obtained by calculation according to a well-known formula from the GD ² of the electric motor rotor system including the rolling roll, the angular acceleration of each case, the back electromotive force, etc. The calculator 7 calculates the rolling current component I _r as I _r =I _n −I _a in accordance with what has already been described.

This rolling current component I _r is compared with a target rolling current component I _t preset by a setting device 10 in a comparator 9, and outputs comparison output signals SC1, SC2, and SC3 according to the following comparison formula. .

SC1=1 when I _r <I _t ...(1) SC2=1 when I _t −α≦I _r ≦I _t +β ...(2) SC3=1 when I _r >I _t ...(3 ) Comparison output signals not listed in each equation are zero.

The target rolling current component I _t may be, for example, the rated current value of the electric motor 2, and α and β in equation (2) are the lower allowable range and upper allowable range for current control with respect to the target rolling current component I _t .

According to the combination of the comparison output signal from the comparator 9 and any one of the accelerating (A), decelerating (D), and constant speed rolling (H) signals representing the respective rolling state, the logic circuit 11 operates as follows. Relay 12
Alternatively, 13 and 14 are selectively energized. Note that the relays 12, 13, and 14 are used for acceleration, constant speed maintenance, and deceleration, respectively.

(4)...SC1∩H→energize the acceleration relay 12 (5)...(SC2∩A)∪(SC1∩D)∪(SC3∩A)
→ energizes constant speed holding relay 13 (6)...SC3∩H → energizes deceleration relay 14 In the apparatus shown in Fig. 1, the rolling speed setting device 2 shown in Fig. 2
0 is provided with a maximum speed setting device 15, and the acceleration command contact 23 is connected to this maximum speed setting device 1.
It is connected to the output side of 5.

The make contact 12a of the relay 12 forms a parallel shunt to the acceleration command contact 23, and similarly the make contact 13a of the relay 13 forms a parallel shunt to the constant speed hold command contact 25, and the make contact 1 of the relay 14 forms a parallel shunt to the acceleration command contact 23.
4a are connected to the deceleration command contact 24 so as to form a parallel shunt, respectively. moreover,
The acceleration command contact 23 includes break contacts 13b1 of the constant speed holding relay 13 and deceleration relay 14,
14b1 is connected in series for interlock, and similarly, acceleration relay 1 is connected to deceleration command contact 24.
2 and the break contacts 12b1 and 13b2 of the constant speed holding relay 13 are connected in series, and the constant speed holding command contact 25 has the break contacts 12b2 and 14b2 of the acceleration relay 12 and the deceleration relay 14.
are connected in series. The components designated by numerals 20-26 are the same as those described with reference to FIG. The output signal of the function generator 22 is compared with the speed signal from the speed detector 4 as a speed reference, and the speed of the electric motor 2 is controlled via the speed control device 5 and the power converter 3 so that the deviation becomes zero. be done.

According to the circuit configuration shown in FIG. 1, the maximum rolling speed is always set as the maximum speed by the maximum speed setting device 15 instead of the speed setting by the operator using the rolling speed setting device 20 in the apparatus shown in FIG. In principle, first, the acceleration command contact 23, deceleration command contact 24, constant speed hold command contact 25, and stop command contact 26 are selectively turned on according to the rolling schedule, and acceleration, deceleration, constant speed maintenance, and stopping are performed accordingly. Perform the action. The current detector 6 detects the current I _n flowing through the motor 2, and the calculator 7 subtracts the acceleration/deceleration current component I _a from the current I _n to obtain the rolling current component I _r . This rolling current component I _r is compared with the target rolling current component I _t by a comparator 9, and comparison output signals SC1 to SC3 are output according to equations (1) to (3). The logic circuit 11 makes logical judgments of equations (4) to (6) based on comparison output signals SC1 to SC3 and the respective rolling state signals A, H, and D, and selects one of equations (4) to (6). Relay 12 when satisfied
-14 is energized. For example, assume that equation (4) is satisfied. In this case, I _r < I _t and the constant speed is being maintained (H), and the acceleration relay 12
is energized. In other words, satisfying equation (4) means that the rolling current component I _r is smaller than the target rolling current component I _t and there is still some margin in the motor 2, so the relay 12 is energized, The break contact 12b2 in series with the constant speed holding contact 25 is turned off to invalidate the constant speed holding command, and the make contact 12
Turn on a and issue an acceleration command. As a result, the set value signal of the maximum speed setter 15 is introduced to the function generator 22, and the function generator 22 gradually increases the speed reference toward the maximum speed. Rolling current component of electric motor 2
I _r is monitored in real time, and when it no longer satisfies equation (4), that is, when I _r =I _t , for example, the signal SC1 becomes zero and the signal SC2 becomes 1. This turns off relays 12-14 and therefore contacts 1
2a is also turned off, and constant speed maintenance contact 2 is turned off as originally.
5, a constant speed holding operation is performed.

Similarly, assume that the relay 13 is energized under the condition (SC2∩A). in this case,
This means that the acceleration is in progress and I _t −α≦I _r ≦I _t +β.The break contact 13b1 in series with the acceleration command contact 23 is turned off to invalidate the acceleration command, and the make contact 13a is set to be on. Performs speed holding operation. This prevents overcurrent, that is, overload, when the acceleration operation continues via the acceleration command contact 23 while maintaining the operation of the electric motor 2 at its full capacity.

Next, there is a case where the deceleration relay 14 is energized by satisfying equation (6). In this case, I _r > I _t , that is, the constant speed is maintained even though there is an overcurrent condition, and the brake Turn off the contact 14b2 to invalidate the constant speed hold command by the constant speed hold command contact 25,
By turning on the make contact 14a, the function generator 22
will generate a speed reference that gradually decreases toward the low speed setting value by the low speed setter 21 via the low speed setter 21. When the rolling current component I _r leaves the range of equation (6), the relay 14 is turned off and the constant speed holding operation starts via the initial constant speed holding command contact 25 .

As described above, by focusing on the rolling current component obtained by subtracting the acceleration/deceleration current component of the electric motor 2, it automatically maintains operation at its full capacity without causing it to become an overcurrent or, conversely, an undercurrent. can do.

Note that the electric motor 2 may be either a DC motor or an AC motor. Correspondingly, the power converter 3 may also have an AC output, that is, an inverter or a cycloconverter, or a DC output, that is, a rectifier or a chopper.

〔Effect of the invention〕

According to the present invention, the current flowing through the rolling mill driving motor is considered separately into a short-time transient acceleration/deceleration current component and a constantly necessary rolling current component, and the latter rolling current component is set to a predetermined value. Since the speed is controlled to ensure that the motor is fully utilized for rolling, it prevents interruptions in operation due to overload, etc., improving the operating rate, and eliminates the need for speed settings by the operator. , it is possible to prevent accidents caused by human erroneous operation.

[Brief explanation of drawings]

FIG. 1 is a block wiring diagram of a control device for a rolling mill driving motor according to an embodiment of the present invention, and FIG. 2 is a block wiring diagram of main parts of a conventional control device. DESCRIPTION OF SYMBOLS 1... Rolling roll, 2... Rolling mill driving electric motor, 3... Power converter, 4... Speed detector, 5...
...Speed control device, 6...Current detector, 7...Calculator, 8...Acceleration/deceleration current calculator, 9...Comparator, 1
0... Setting device, 11... Logic circuit, 12... Acceleration relay, 13... Constant speed maintenance relay, 14...
Deceleration relay, 15... Maximum speed setting device, 21...
...Low speed setting device, 22...Function generator, 23...
...Acceleration command contact, 24...Deceleration command contact, 25...
...Constant speed hold command contact, 26...Stop command contact.

Claims (1)

[Scope of Claims] 1. A control device for a rolling mill driving motor that controls the speed of a rolling mill driving motor at a predetermined acceleration/deceleration rate so as to match a speed standard according to a rolling schedule, comprising: a current for detecting the current of the motor; detection means;
a calculation means for obtaining a rolling current component by subtracting an acceleration/deceleration current component required for acceleration/deceleration of the motor from the current detected by the current detection means; and a target rolling current component setting means for setting a target value for the rolling current component. a comparison means for comparing the rolling current component and the target value and outputting a comparison output signal according to the magnitude relationship between the two; and a rolling status signal indicating whether the rolling mill is accelerating, decelerating, or constant speed. Logic means that makes a logical judgment according to the combination with the comparison output signal and outputs an acceleration command, constant speed holding command, or deceleration command;
and speed reference setting means for setting a speed reference for the speed control system of the electric motor within a range between a predetermined low speed and a maximum speed according to the output of the logic means. Control device for electric motors.