JPH01186191A - Motor controller - Google Patents

Abstract

PURPOSE:To attain the rise of speed in a short time by selectively using a speed reference from a speed setting means and the feedback value of speed through a rate control means as an input speed reference used in a speed control means. CONSTITUTION:A rate limiting circuit 30 is provided as a speed reference input means of a speed control circuit 21. A changeover circuit 31 conducts changeover operation so as to respectively send a speed reference to a speed control circuit 22 from a speed setter 20 during the normal operation of a control system and the feedback value of speed from a speed detector during the stoppage of the control system through the rate limiting circuit 30 as speed references of the speed control circuit 22. Accordingly, speed is made to rise in a short time without generating commutation failure when the control of a motor is started during the revolution of the motor or in resumption from instantaneous service interruption, thus safely operating the motor efficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an electric motor control device including a speed control means for feedback controlling the speed of an electric motor according to a speed reference.

(Prior Art) As a control device for a variable speed controlled electric motor, one having the configuration shown in FIG. 4 is known. In the device shown in Figure 4,
Rectifier 10, DC reactor 11, and inverter 12
An alternating current voltage of variable frequency and variable voltage is supplied to the synchronous motor 13 via the synchronous motor 13 . A field current is supplied to the field winding 14 via a frequency converter 15, an AC exciter 16, and a rotary rectifier F.

The frequency converter 15, the AC exciter 16, and the rotary rectifier 17 constitute a brushless exciter. Synchronous electric machine 1
Voltage 3 and speed Q are detected by voltage detector 18 and speed detector 19, respectively, and guided to the control circuit. In addition, the speed control circuit 2 is configured so that the deviation between the zero speed reference set by the speed setting 1120 and the speed feedback ω detected by the speed detector 19 is zero.
1 controls the armature current reference Ia''.

Armature current Ia is detected by current detection@22 and controlled by armature current control circuit 23 to match armature current reference I-. The speed of the synchronous motor 13 is controlled by this armature current Ia.

On the other hand, based on the voltage V detected by the voltage detector 18 and the speed ω detected by the speed detector 19, the arithmetic unit 24 obtains a feedback value of the field magnetic flux φ as φ=f(V/ω). On the other hand, a magnetic flux reference φ8 is set by the magnetic flux setter 25, and is a field current reference for making the deviation between the magnetic flux reference φ east and the field magnetic flux φ zero. If" is formed by the magnetic flux control circuit 26. The field current If flowing through the field winding 14 is detected by the current detection base 27 on the primary side of the frequency converter W15, and is adjusted to match the field current reference If". Feedback control is performed via the field current control circuit 28 and the frequency converter 15. The magnetic flux of the periodic motor 13 is controlled by such field current control.

(Problem to be Solved by the Invention) However, the conventional motor control device described above has the following problem when the control circuit starts operating while the motor is rotating when a momentary power outage occurs. . This is the fifth
This will be explained with reference to the figures and FIG. Now, in FIG. 5, it is assumed that a momentary power outage occurs at point a and is restored at point b. At this time, if the control is stopped at point a and restarted at point b, the speed ω decreases in accordance with the inertia of the rotating body and the load torque, so it is far away from the speed reference zero line.

Therefore, the output of the speed control means, which is the armature current reference Ia'', increases rapidly. On the other hand, the field magnetic flux φ decreases from point C according to the motor time constant, and the armature current that can be commutated by the inverter increases in proportion to it. Because Ia decreases, the fifth
As shown in the figure, if an excessive current is passed during a period when the magnetic flux is weakening, there is a risk that the commutation of the inverter 12 will fail.

Therefore, in the conventional motor control device, as shown in FIG. 6, speed control is started after waiting until point C, at which the magnetic flux φ recovers to the level before the instantaneous power outage. Even though the instantaneous power outage ends at point B, armature current control actually begins to operate at point C.
Control waste time occurs over a long period of time from point b to point C.

Therefore, in variable speed drive devices used in plant equipment, etc., it is often required to return to a steady state in a short time after a momentary power outage occurs, so the above control state is inconvenient (protective). .

Therefore, an object of the present invention is to achieve a speed rise in a short time without causing commutation failure in the inverter when the speed control system changes from OFF to ON while the motor is rotating in the event of a momentary power outage. The object of the present invention is to provide a motor control device that enables safe and efficient operation.

[Structure of the invention]

(Means for Solving Problem 11) The present invention provides a motor control device having a speed control means for feedback controlling the speed of a synchronous motor according to a speed reference, in which a rate a limiting means, and a setting value set by the speed setting means during steady operation as the speed reference, and a feedback value of the motor speed is switched to the input side of the rate limiting means when the speed control function is stopped. A motor control device is provided that includes a switching device and a limiting device that varies a limiting value of an armature current reference according to a value of field magnetic flux of the motor.

(Function) According to the above configuration, the rate limiting means effectively acts on the speed reference in the speed control only when one part of the control circuit system is turned off, and becomes substantially ineffective during steady operation. Furthermore, since the armature current is limited according to the field magnetic flux, when the speed control system changes from off to on,
The inverter can achieve a speed rise in a short time without commutation failure, and can perform safe and efficient operation.

(Example) FIG. 1 shows an embodiment of the present invention.

This device is based on the circuit configuration of the device shown in FIG. 4, and includes a rate limiting circuit 30, a switching circuit 31, and a current limiting circuit 3.
This corresponds to the addition of 2 and 2. The rate limiting circuit 30 is provided in the speed reference input means of the speed control circuit 21. The switching circuit 31 uses the speed reference from the speed setter 20 as the speed reference to the speed control circuit 22 during normal operation of the control system, and the feedback value of speed ω from the speed detector 19 when the control system is stopped. The switching operation is performed so that the signals are respectively guided through the rate limiting circuit 30.

Further, the current limiting circuit 32 operates to limit the armature current reference knee according to the field magnetic flux φ.

The operation of the circuit device shown in FIG. 1 will be explained with reference to FIG. 2. FIG. 2 shows a time chart when a momentary power outage occurs at point a and recovery occurs at point b. Synchronous motor 13
The feedback values of the speed ω and the field magnetic flux φ are gradually decreasing from point a, but since the control function is stopped during a momentary power outage, the switching circuit 31 changes the speed reference 0 quintillion to the feedback value of the speed ω. remains the same value. When the control function is restored at point b, the switching circuit 31 switches the speed setting device 20
By switching to the side, the speed reference 0 bundle is set to the speed setter 2.
According to the setting standard of 0, it gradually increases with a rising edge determined by the characteristics of the rate limiter 30, and finally reaches the set value of the speed setter 20. In other words, since the speed reference 0 flux is changed gradually rather than stepwise from point b where control starts, there is no need for an excessive current reference knee to follow the feedback value of speed ω, and furthermore, Since the armature current reference Ia' is limited according to the value of the field magnetic flux φ, there is no risk of commutation failure of the inverter 12.

In this way, problems such as the inconvenience caused by the decrease in magnetic flux φ and the time it takes for the current reference Ia to occur after control is started can be solved, and the problem can be shortened without commutation failure. The speed can be increased in a short amount of time and the motor can be operated safely and efficiently.

Note that the frequency converter 15 and AC exciter 1 in FIG.
6, and instead of the rotary rectifier 17, a field rectifier 33 may be used as shown in FIG. 3. With this configuration as well, the same effect as that in FIG. 1 can be achieved. .

Note that the arithmetic control circuit portion in the above embodiments can also be realized by computer software.

〔Effect of the invention〕

According to the present invention, control is started while the motor is rotating by selectively using the speed reference from the speed setting means and the speed feedback value as the input speed reference to the speed control means via the rate control means. When the power is restored after a momentary power outage, the speed can be increased in a short time without commutation failure, and the motor can be operated safely and efficiently.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a time chart for explaining the action of the device shown in Fig. 1 during momentary power outage, and Fig. 3 is a block diagram showing a modification of the present invention. 4 are block diagrams of a conventional field control device for a synchronous motor, and FIGS. 5 and 6 are time charts for explaining the operation of the device shown in FIG. 4. 13...Synchronous motor 14...Field winding 1
9...Speed detector 20...Speed setter 2
1...Speed control circuit 30...Rate limiting circuit 31...Switching circuit Agent Patent attorney Noriyuki Chika Ken Yudo Daishimaru Ken Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] In a motor control device having a speed control means for feedback controlling the speed of an electric motor based on a speed reference, a rate limiting means is provided before a speed reference input means of the speed control means and makes the speed reference have predetermined characteristics. and a switching means for switching the speed reference so as to guide the setting value set by the speed setting means during steady operation and the feedback value of the motor speed when the control function is stopped to the input side of the rate limiting means. and a limiting means for limiting the output of the speed controlling means according to the field magnetic flux.