JPH01177897A - Speed controller for motor - Google Patents

Abstract

PURPOSE:To attain quick start and stopping by conducting compensation corresponding to a maximum adjustable speed rate capable of increasing or decreasing the speed of each motor while each motor is coordinated on the basis of the state of load of respective motor. CONSTITUTION:Motor currents I1, I2, I3 flowing through motors 3a, 3b, 3c are detected at every motor through current detectors 5a, 5b, 5c, and introduced to an adjustable speed controller 7. The adjustable speed controller 7 arithmetically operates speed reference compensation-quantity v on the basis of motor currents I1, I2, I3. The speed reference compensation-quantity v is subtracted from a speed reference V0 in order to compensate the speed reference V0 from a speed reference setter 4, and a compensation speed reference VS=V0- v acquired as the difference is given to each speed controller 1a, 1b, 1c.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention is directed to an electric motor that controls a plurality of electric motors, each of which has its own drive target connected, so as to drive them in synchronization with each other according to a speed standard. The present invention relates to a speed control device, for example, a motor speed control device suitable for simultaneously accelerating and decelerating a plurality of motors that cooperatively drive a plurality of rolls in a continuous rolling line or a continuous processing line.

(Prior Art) FIG. 4 shows a speed control device for an electric motor that has been commonly used in the past. This device exemplifies a speed control system in a continuous processing rolling line having a plurality of stands.
, 3b.

It is configured to be driven individually by 3C. Each electric motor 3a, 3b, 3c has a corresponding drive device 2a.
, 2b, 2c.

These drives consist of power converters, which receive power from an alternating current power supply AC and supply regulated power to the associated electric motor. Drive device 2a.

Speed controller 1a to control 2b, 2c.

lb and lc are provided. Speed controller 1a.

A speed reference Vo is given to lb and lc from the speed reference setter 4, and the speed reference V is the speed of the electric motors 3a, 3b, and 3c.

Speed controller 1a to match.

Speed control of electric motors 3a, 3b, 3c is performed via lb, lc and drive devices 2a, 2b, 2c. The speed control system in this case is an open loop control system.

In the speed control device shown in Fig. 4, each roll BRI, BR
2. When the BR3 accelerates or decelerates, that is, when starting acceleration from a stopped state to a constant speed state or when decelerating and stopping from a constant speed state to a stopped state, the speed reference setting device 4 sets the same acceleration/deceleration rate (
Speed standard V (temporal change rate of acceleration/deceleration is constant). is issued, and the motors 3a, 3b, 3c have their speed reference V. The speed will be controlled according to the following.

(Problems to be Solved by the Invention) In the conventional speed control device illustrated in FIG. 4, the acceleration/deceleration rate set in the speed reference setting device 4 is
, 3c, the maximum acceleration/deceleration rate that is capable of being performed for each electric motor is determined from the normally expected load, and the one with the smallest value is selected from among them. This makes it possible to cooperatively start or stop all the electric motors 3a to 3C in a relatively short time without any support.

However, conventional motor speed control devices do not rely on feedback control and use fixed acceleration/deceleration rates to control the speed, and depending on the material and the state of tension between the motors, the startup time or stoppage time may be shorter within the motor's capacity. Even if it is possible to control the speed at an acceleration/deceleration rate that takes a certain amount of time, the result is that a relatively long acceleration/deceleration time is required.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a speed control device for an electric motor that can solve the problems of the prior art described above and achieve faster acceleration and deceleration during starting and/or stopping.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a plurality of current detection means provided for each motor, and a current detection means for each motor based on the motor current detected by these current detection means. A load state calculation means for calculating the load state of the electric motor, and a speed reference correction amount corresponding to a maximum acceleration/deceleration rate at which each electric motor can be accelerated or decelerated while coordinating each motor based on the load state of each motor determined by the load state calculation means. The present invention is characterized by comprising a speed reference correction amount calculation means for calculating, and means for correcting the speed reference by the speed reference correction amount.

(Function) In the motor speed control device of the present invention, the current flowing through a plurality of motors is detected, and the load state of each motor is detected from this value. When the current flowing through the motor is relatively small compared to the acceleration/deceleration current limit value, the correction amount is increased via the speed reference correction amount calculation means to obtain a larger acceleration/deceleration rate, and conversely, the current flowing through the motor is the acceleration/deceleration current. The closer the limit value is, the more the correction amount is reduced to suppress the acceleration/deceleration rate. By controlling in this manner, it is possible to achieve the maximum possible acceleration/deceleration rate within the capability range of the electric motor each time, and to achieve faster starting control and/or stopping control.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a speed control device for an electric motor according to an embodiment of the present invention. Electric motors 3a, 3b.

Motor current flowing through 3c, 11. I2. I3 is a current transformer 6a on the power supply side of the drive devices 2a, 2b, and 2c.

6b, 6c and current detectors 5a, 5b, 5c for each electric motor, and is introduced into the acceleration/deceleration controller 7. The acceleration/deceleration controller 7 controls the motor current to 11°■2. A speed reference correction amount ΔV is calculated based on I3. This speed reference correction amount ΔV is the speed reference V from the speed reference setting device 4. The corrected speed reference vS-vo-ΔV obtained as the difference is subtracted from the speed reference Vo in order to correct the difference, and is calculated by each speed controller 1a,
lb.

given to IC.

As is clear from the above description, the present invention is applicable to both acceleration control during startup and deceleration control during stopping, but acceleration and deceleration are treated as algebraic differences in sign. Therefore, a more specific explanation will be given below, taking the case of deceleration control at the time of stopping as an example.

Motor current manually inputted to acceleration/deceleration controller 7 11°■2. I
3 are not necessarily the same, but are compared with the deceleration side current limit value I, and the current deviation ΔI −I −II
l ・・・・・・(1) Ig l ΔI −I −II l ・・・・・・(
2) 2g 2 ΔI −1−II + ・・・・・・(3)
3g 3 are the load state calculators 71a and 71b shown in FIG.

71c. This current deviation becomes an index representing the load condition of each motor. Among these current deviations, the one with the minimum value is detected by the maximum load calculator 72 as the minimum current deviation ΔI.

The motor corresponding to this minimum current deviation ΔI is under the most excessive load condition. This current deviation ΔI
is relatively large, it means that there is still some margin in the load capacity of all the motors 3a to 3C, including the motor concerned, and the speed reference correction amount calculator 73 increases the speed reference correction amount ΔV, i.e. , control is performed in the direction that results in greater deceleration. Conversely, as the minimum current deviation ΔIx approaches zero, this means that the motor is being operated under the most severe load conditions, which means that the motor is approaching the state where overload tripping is most likely to occur. Therefore, the speed reference correction amount calculator 73 acts in the direction of reducing the speed reference correction amount ΔV. As a result, the modified speed standard V
approaches the speed reference VO from the speed reference setter 7, and therefore the speed reference V for the speed controllers 1a-IC.

A modified speed reference V 2 with a deceleration rate close to the deceleration rate of V is given. Minimum current deviation ΔI and speed reference correction amount ΔV
An example of the relationship is shown in Figure 3.

By modifying the deceleration rate as described above, it is possible to decelerate at the maximum possible deceleration rate and achieve a stop in the shortest possible time without avoiding a trip due to overload.

In the above embodiment, the case of deceleration and stop has been explained, but as already stated, the present invention is applicable to the case of acceleration and start. In that case, the speed reference correction amount Δ■ will be output with the opposite sign to that in the case of deceleration.
Depending on the magnitude, the speed reference V 1 is modified to have a larger value, that is, a larger acceleration rate.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to accelerate and decelerate at the maximum possible acceleration and deceleration rate, thereby achieving quick start and stop.

[Brief explanation of the drawing]

1 is a block diagram of a speed control device according to an embodiment of the present invention, FIG. 2 is a block diagram showing a specific configuration example of an acceleration/deceleration controller in the device of FIG. 1, and FIG. 3 is a block diagram of a speed control device according to an embodiment of the present invention. A characteristic diagram for explaining the action of the acceleration/deceleration controller in the device, FIG. 4 is a block diagram of a conventional speed control device. BRI, BH3, BH3-ol, la, lb. IC...Speed controller, 2a, 2b, 2c...Drive device, 3a, 3b, 3c...Electric motor, 4...Speed reference setter, 5a, 5b, 5c-Current detector , 6a. 6b, 6c... Current transformer, 7... Acceleration/deceleration controller. Applicant's agent Mr. Sato

Claims (1)

[Scope of Claims] A speed control device for a motor that controls a plurality of motors each connected to a unique drive target so as to drive them in synchronization with each other according to a speed standard, comprising a plurality of current detection means provided for each motor. and a load state calculation means for calculating the load state of each motor based on the motor current detected by these current detection means, and a load state calculation means for coordinating each motor based on the load state of each motor determined by the load state calculation means. an electric motor comprising: speed reference correction amount calculation means for calculating a speed reference correction amount corresponding to a maximum acceleration/deceleration rate that can be accelerated or decelerated while moving; and means for correcting the speed reference by the speed reference correction amount. speed control device.