JPH01270779A - Speed controller for motor - Google Patents

Abstract

PURPOSE:To prevent a motor from hunting or vibrating by reducing a current reference value at a predetermined ratio when the motor is stopped. CONSTITUTION:When a motor stop command is applied from a speed controller 4, a current reference IS output from a current limiting rate calculator 12 is reduced to a predetermined level. Thus, a motor speed is gradually reduced. When the stop of a motor 3 is detected by a speed detector 2, a motor stop signal from a motor speed zero detector 13 is supplied to a current limiting rate calculator 12. The calculator 12 reduces the reference IS at a predetermined ratio simultaneously when the signal is applied. Thus, it can prevent the motor from hunting or vibrating.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a speed control device that can suppress vibrations generated when stopping an electric motor.

(Prior Art) FIG. 3 shows the configuration of a conventional electric motor speed [υ] control device, and this example is for controlling the rotational speed of a rolling roll in a rolling facility.

In the figure, the speed control circuit 4 is supplied with the deviation between the speed reference signal VS given by the speed reference setter 1 and the speed feedback signal V[ of the electric motor 3 obtained from the speed detector 2.

This speed control circuit 4 amplifies the supplied deviation,
Outputs current reference signal.

The current reference signal is limited via a current limiting circuit 5 so that the current supplied to the motor 3 does not become an overcurrent.

The current reference i output from this current limiting circuit 5
s and the motor 3 detected by the motor current detector 6
The deviation from the current value If is determined, and the deviation is supplied to the current control circuit 7.

The current control iM1 circuit 7 controls the gate signal of the thyristor power supply circuit 8 so that this deviation becomes zero.

As a result, the electric motor 3 is supplied with a reference current and rotates at a predetermined speed.

Therefore, the copper strip 10 is rolled at a predetermined speed by the rolling roll 9 connected to the electric motor 3, sent out, and wound up at the winding f111.

When the electric motor [3 controlled in this manner is to be stopped, the current reference circuit 5 limits the current reference 1s according to the characteristics shown in FIG.

When the motor 3 is stopped, the current reference [
is lowered to a certain level, the electric motor 3 is decelerated, and stopped at point B.

At this point B, the current reference IS is set to instantaneously become zero.

(Problem to be Solved by the Invention) As described above, in the conventional example, the current reference is is set to zero at the same time as the electric motor 3 is stopped at point B shown in FIG.

Therefore, with this rapid current change, the torque generated in the electric motor R3 also changes rapidly, and when the electric current flJ13 is stopped, vibrations as shown at point 0 in FIG. 4 occur.

This vibration is transmitted to the rolling roll 9 shown in FIG. 3, and the steel strip 10 is deformed or has an uneven shape due to this imaging.

This invention was made in order to solve these conventional problems, and its purpose is to provide a speed control device for an electric motor that prevents vibrations that occur when stopping the electric motor and allows smooth stopping. Our goal is to provide the following.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a method for achieving zero deviation between the speed reference signal and the speed feedback signal of the motor that is actually being driven. a speed control section that generates a current reference; a motor speed zero detection section that detects that the motor has stopped;
When stopping the electric motor, the current reference supplied from the speed control unit is lowered to zero at a preset constant rate from the time when the electric motor is stopped, which is obtained from the motor speed zero detection unit. It is characterized by comprising a limited rate performance section.

(Function) In the present invention, when stopping the electric motor, the current reference value is lowered at a fixed rate that is stored in advance in the current limit rate calculation section, so that sudden torque fluctuations occurring in the electric motor are suppressed. Ru.

Therefore, hunting and vibration of the motor can be prevented.
It can be stopped smoothly.

(Example) FIG. 1 is a configuration diagram that does not show one embodiment of the present invention.

In the figure, a copper strip 10 is rolled by passing between rotating rolling rolls 9 and wound up! It is wound with fi11.

The rolling roll 9 is connected to an electric motor 113, and its power is transmitted to rotate at a predetermined speed.

The control system for controlling the rotational speed of this electric motor 3 includes a speed reference setting device 1 and an electric! 13, a speed control circuit 4, a current limit rate calculation circuit 12, a motor speed zero detection circuit 13, a current control circuit 7, and a thyristor power supply circuit 8. .

The speed reference setter 1 generates the speed reference signal VS of the electric motor 3, and the speed reference signal VS set by the speed reference setter 1 and the actual speed feedback signal of the electric motor Bff3 obtained from the speed detector 2. The deviation from Vf is determined by speed control circuit 4.
Based on this deviation, an electric m reference signal is generated and supplied to the current limit rate calculation circuit 12.

The current limiting rate worship circuit 12 has the same function as the current limiting circuit 5 shown in the conventional example, but as described later, the electric motor 3
It has the function of lowering the current reference is at a constant rate when stopped.

The current control circuit 7 controls the thyristor power supply circuit 8 by inputting the deviation between the current reference Is output from the current limit rate calculation circuit 12 and the feedback current Wllf actually flowing through the motor 3, and as a result, The electric motor [3] rotates at a predetermined speed.

Next, the operation of this embodiment will be explained with reference to FIG.

FIG. 2 shows the current reference Is output from the current limit rate 'e4 arithmetic circuit 12 and the electric current lll'g! It is a time chart of 1 speed.

When a motor stop command is given from the speed control circuit 4, the current base IIS output from the current limit rate calculation circuit 12
decreases to a certain level (point A in Figure 2). As a result, the speed of the Den-1i71 aircraft gradually decreased and it came to a stop (point B in Figure 2).

When the stop of the electric motor 3 is detected by the speed detector 2 and the detection signal is output to the motor speed zero detection circuit 13, a motor stop signal is supplied from the motor speed zero detection circuit 13 to the current limit rate calculation circuit 12. Ru.

The current limit rate calculation circuit 12 decreases the current reference [S] at a constant rate at the same time as this motor stop signal is given, and therefore, the current reference Is decreases at a constant rate from point B in FIG. 2 to zero. It is reached.

In this embodiment, when the motor stop signal is given to the current limit rate calculation circuit 12, the current reference Is is decreased according to the stop pattern stored in advance, so that the current supplied to the electric motor vIi3 is reduced. It does not change rapidly. Therefore, hunting motion due to sudden changes in the torque generated in the electric motor 3 can be prevented.

As a result, the rolling roll 9 is smoothly stopped, and defects such as deformation and uneven shape of the copper strip 10 can be prevented.

[Effects of the Invention] As described above, in the present invention, a current limit rate PiA section is provided, and when the motor stops, the current reference is lowered at a constant rate set in the current limit rate section q. Therefore, as shown in the conventional example, the current value supplied to the motor does not change suddenly, and hunting and vibration caused by this can be prevented from occurring.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
FIG. 3 is a configuration diagram showing a conventional example, and FIG. 4 is a time chart of the current reference IS and flXall speed in FIG. 3. 3... Electric motor 9... Roll roll 12.
...Current limit rate calculation circuit 13...Motor speed zero detection circuit

Claims (1)

[Scope of Claims] A speed control section that generates a current reference so that the deviation between the speed reference signal and the speed feedback signal of the motor that is actually being driven becomes zero, and that detects that the motor has stopped. a motor speed zero detection section; and when stopping the motor, a current reference is supplied from the speed control section at a preset constant rate from the time when the motor stops, which is obtained from the motor speed zero detection section. A speed control device for an electric motor, comprising: a current limit rate calculation unit that reduces the current limit rate to zero;