JPH06253576A - Motor controller - Google Patents

Abstract

PURPOSE:To allow driving of an induction motor at a highest efficiency point at all times by controlling the slip frequency for correcting the torque of the induction motor depending on a voltage command to be applied to the induction, motor. CONSTITUTION:A slip frequency signal 10 is initially set at a constant f0. The slip frequency 10 is shifted by a slight amount fX to a frequency f1 during an interval when a speed command signal 13 is shifted to a predetermined value which is sustained until the rotational speed of an induction motor 1 is sufficiently settled. Although r.p.m. of the induction motor 1 is varied to cause variation of a speed feedback signal 9, the speed feedback signal 9 is controlled to be identical with the speed command signal 13 so that the induction motor 1 has r.p.m. corresponding to the speed command signal 13. This constitution allows the induction motor to be driven at a highest efficiency point at all times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor controller for an induction motor, which controls the coil voltage of the motor by PWM.

[0002]

2. Description of the Related Art In recent years, PWM inverters have rapidly spread and are widely used for motor control.

A conventional motor control device will be described below. FIG. 2 is a schematic diagram of a conventional electric motor control device, showing a three-phase induction motor as an example. Generally, the number of the voltage signals 16 of the PWM inverter control circuit 8 varies depending on the number of phases of the induction motor, but the basic operation is the same.

In FIG. 2, 1 is an induction motor, 2 is a speed sensor that detects the rotation speed of the shaft of the induction motor 1 and outputs a speed feedback signal 9, and 6 is a speed command signal 13 that sets the rotation speed of the induction motor 1. A speed error detection means for inputting the speed feedback signal 9 and outputting a speed error signal 14 obtained by amplifying an error between the speed command signal 13 and the speed feedback signal 9, and 7 for inputting the speed error signal 14 and the speed error signal 14 being negative. It is a voltage command generating means for outputting a voltage command signal 15 according to the speed error signal when 0, 0 or positive.

Further, 3 is a slip frequency generating means for outputting a slip frequency signal 10, 4 is a speed / frequency converting means for inputting a speed feedback signal 9 and outputting a synchronizing frequency signal 11, 5 is a slip frequency signal 10 and a synchronizing frequency. The frequency addition means for inputting the signal 11 and outputting the basic frequency command signal 12 which is the addition signal of the slip frequency signal 10 and the synchronous frequency signal 11, and 8 for inputting the voltage command signal 15 and the basic frequency command signal 12 receives the induction motor 1 It is a control circuit for a PWM inverter that outputs a voltage signal 16 supplied to the.

The operation of the electric motor control device configured as described above will be described below. In FIG. 2, first, the speed command signal 13 is 0 and the speed feedback signal 9 starts from an initial state of 0, the speed command signal 13 is changed to a predetermined value, and the value is held. Thereby, the speed error detecting means 6 outputs the speed error signal 14 obtained by multiplying the error between the speed command signal 13 and the speed feedback signal 9 by a predetermined constant. By inputting this speed error signal 14, the voltage command generating means 7 generates a voltage command signal 15 according to the speed error signal 14, and the PWM inverter control circuit 8 outputs a voltage signal 16 to be supplied to the induction motor 1. Come to do. As a result, the induction motor 1 starts to rotate and the speed feedback signal 9 increases.

When the speed feedback signal 9 is generated, a synchronous frequency signal 11 proportional to the speed feedback signal 9 is output at the same time, and the synchronous frequency signal 11 is provided for correcting the torque of the induction motor 1 by the frequency adding means 5. The basic frequency command signal 12 is output by adding to the slip frequency signal 10 thus obtained. The slip frequency signal 10 has a predetermined constant, and is generally set to about 5 Hz. The basic frequency command signal 12 together with the voltage command signal 15 pass through the PWM inverter control circuit 8 and the induction motor 1
The rotational speed of the induction motor 1 is controlled according to the speed command signal 13 by controlling the rotational speed of the induction motor 1 so that the speed feedback signal 9 matches the speed command signal 13.

[0008]

However, in the above conventional structure, since the slip frequency is a predetermined constant, the induction motor is not affected by variations in characteristics of the induction motor, variations in control circuit components, changes in ambient temperature, and the like. However, there is a problem that it cannot always be driven at the highest efficiency point.

The present invention solves the above-mentioned conventional problems, and can always drive the induction motor at the highest efficiency point against variations in characteristics of the induction motor, variations in control circuit components, changes in ambient temperature, and the like. An object of the present invention is to provide a motor control device.

[0010]

To achieve this object, an electric motor control device of the present invention comprises an induction motor, a speed sensor for constantly measuring the rotational speed of the shaft of the induction motor, and outputting a speed feedback signal. Speed error detecting means for inputting a speed command signal for setting the rotation speed of the induction motor and the speed feedback signal and outputting a speed error signal obtained by amplifying an error between the speed command signal and the speed feedback signal, and the speed error. A voltage command generating means for inputting a signal and outputting a voltage command signal corresponding to the speed error signal, a slip frequency generating means for inputting the voltage command signal and outputting a slip frequency signal, and a speed feedback signal for synchronization by inputting A speed / frequency conversion means for outputting a frequency signal, and the synchronization frequency signal and the slip frequency signal are input. A frequency adding means for outputting a basic frequency command signal which is an addition signal of the synchronous frequency signal and the slip frequency signal, and the voltage command signal and the basic frequency command signal are input and a voltage signal supplied to the induction motor is output. It has a configuration including a PWM inverter control circuit.

[0011]

With this configuration, by controlling the slip frequency for correcting the torque of the induction motor according to the voltage command applied to the induction motor, the induction motor can always be driven at the highest efficiency point.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is an induction motor, 2 is a speed sensor which detects the rotation speed of the shaft of the induction motor 1 and outputs a speed feedback signal 9, 6 is a speed command signal 13 which sets the rotation speed of the induction motor 1, and The speed error detection means 7 inputs the speed feedback signal 9 and outputs the speed error signal 14 obtained by amplifying the error between the speed command signal 13 and the speed feedback signal 9, and 7 inputs the speed error detection means 14 and the speed error signal 14 is negative. The voltage command generating means outputs a voltage command signal 15 corresponding to the speed error signal when 0, 0 or positive.

Reference numeral 3 is a slip frequency generating means for inputting the voltage command signal 15 and outputting a slip frequency signal 10 in response to the voltage command signal 15. Reference numeral 4 is for inputting a speed feedback signal 9 and outputting a synchronizing frequency signal 11. The speed / frequency conversion means 5 inputs the slip frequency signal 10 and the synchronous frequency signal 11, and the basic frequency command signal 12 which is the addition signal of the slip frequency signal 10 and the synchronous frequency signal 11.
Is a frequency adding means for outputting the voltage command signal 15 and the basic frequency command signal 12 and is a PWM inverter control circuit for outputting a voltage signal 16 to be supplied to the induction motor 1.

The operation of the electric motor control device configured as described above will be described below. In FIG. 1, first, the speed command signal 13 is 0, and the speed feedback signal 9 starts from an initial state of 0. Then, the speed command signal 13 is changed to a predetermined value, and the value is held. Thereby, the speed error detecting means 6 outputs the speed error signal 14 obtained by multiplying the error between the speed command signal 13 and the speed feedback signal 9 by a predetermined constant. By inputting this speed error signal 14, the voltage command generating means 7 generates a voltage command signal 15 according to the speed error signal 14, and the PWM inverter control circuit 8 outputs a voltage signal 16 to be supplied to the induction motor 1. Come to do. As a result, the induction motor 1 starts to rotate and the speed feedback signal 9 increases.

When the speed feedback signal 9 is generated, the synchronous frequency signal 11 proportional to the speed feedback signal 9 is simultaneously output, and the synchronous frequency signal 11 is provided for correcting the torque of the induction motor 1 by the frequency adding means 5. The basic frequency command signal 12 is output by being added to the slip frequency signal 10 output according to the voltage command signal 15.

The basic frequency command signal 12 is the voltage command signal 1
5, the rotation speed of the induction motor 1 is changed through the PWM inverter control circuit 8 and the speed feedback signal 9 is controlled to match the speed command signal 13. I am supposed to.

Although the speed error detecting means 6 is described as a proportional amplifier, the same operation can be obtained by using the speed error detecting means 6 as a proportional-plus-integral amplifier.

The operation of the slip frequency generating means 3 will now be described in detail. The slip frequency signal 10 is set to a predetermined constant f0 in the initial state. At time T1 when the speed command signal 13 changes to a predetermined value and the value is held and the rotation speed of the induction motor 1 becomes sufficiently constant,
The slip frequency signal 10 is set to a frequency f1 which is obtained by adding a predetermined small frequency fx to f0. By changing the slip frequency signal 10, the rotation speed of the induction motor 1 changes and the speed feedback signal 9 changes, but the speed feedback signal 9 and the speed command signal 13 are controlled to be the same, and the induction motor 1 is controlled by the speed command signal. The rotation speed corresponds to 13.

At the time T2 when the rotational speed of the induction motor 1 becomes sufficiently constant again, the voltage command signal 15 at the time T1 and the voltage command signal 15 at the time T2 are compared, and the time T2 is compared.
If the voltage command signal 15 at 1 is greater than the voltage command signal 15 at time T2, the slip frequency signal 10
To the voltage command signal 1 at time T2
If 5 is larger than the voltage command signal 15 at time T1, the frequency −fx is added to the slip frequency signal 10. By changing the slip frequency signal 10 again, the rotation speed of the induction motor 1 changes and the speed feedback signal 9 changes, but the speed feedback signal 9 and the speed command signal 1
3 are controlled to be the same, and the induction motor 1 has a rotation speed corresponding to the speed command signal 13.

At time T3 when the rotation speed of the induction motor 1 becomes sufficiently constant again, the voltage command signal 15 at time T2 and the voltage command signal 15 at time T3 are compared, and the time T3 is compared.
If the voltage command signal 15 at 2 is larger than the voltage command signal 15 at time T3, the slip frequency signal 10 is again detected.
To the voltage command signal 1 at time T3
If 5 is larger than the voltage command signal 15 at the time T2, the frequency -fx is added to the slip frequency signal 10 again.

Thereafter, the same operation is repeated, and the slip frequency generating means 3 outputs the slip frequency signal 10 according to the voltage command signal 15. However, slip frequency signal 10
The output frequency range is set so that the induction motor 1 does not cause an abnormal operation by the slip frequency signal 10.

[0023]

As described above, the present invention includes an induction motor,
A speed sensor that constantly measures the rotation speed of the shaft of the induction motor and outputs a speed feedback signal, a speed command signal that sets the rotation speed of the induction motor, and the speed feedback signal are input, and the speed command signal and the speed are input. A speed error detecting means for outputting a speed error signal obtained by amplifying an error of a feedback signal; a voltage command generating means for inputting the speed error signal and outputting a voltage command signal according to the speed error signal; A slip frequency generating means for inputting and outputting a slip frequency signal, a speed / frequency converting means for inputting the speed feedback signal and outputting a synchronizing frequency signal, and a synchronizing frequency signal for inputting the synchronizing frequency signal and the sliding frequency signal And the frequency addition that outputs the basic frequency command signal that is the addition signal of the slip frequency signal. Means and the inputs a voltage command signal and the fundamental frequency command signal, by a configuration in which a control circuit for a PWM inverter for outputting a voltage signal supplied to the induction motor, an induction motor of variation,
It is possible to realize an excellent electric motor control device that can always drive the induction motor at the optimum efficiency point even if variations in control circuit components and changes in ambient temperature occur.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a motor control device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a conventional motor control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 induction motor 2 speed sensor 3 slip frequency generating means 4 speed / frequency converting means 5 frequency adding means 6 speed error detecting means 7 voltage command generating means 8 PWM inverter control circuit

Claims (2)

[Claims] 1. An induction motor, a speed sensor for constantly measuring a rotation speed of a shaft of the induction motor and outputting a speed feedback signal, and a speed command signal and the speed feedback signal for setting a rotation speed of the induction motor. A speed error detection means for outputting a speed error signal obtained by amplifying an error between the speed command signal and the speed feedback signal; and a voltage command for inputting the speed error signal and outputting a voltage command signal corresponding to the speed error signal. Generating means, slip frequency generating means for inputting the voltage command signal and outputting a slip frequency signal, speed / frequency converting means for inputting the speed feedback signal and outputting a synchronous frequency signal, the synchronous frequency signal and the slip A fundamental frequency that is a sum signal of the synchronization frequency signal and the slip frequency signal by inputting a frequency signal A frequency adding means for outputting a command signal and a PWM inverter control circuit for inputting the voltage command signal and the basic frequency command signal and outputting a voltage signal to be supplied to the induction motor are provided. First, the induction motor is stopped. In the initial state, the slip frequency signal is set to a predetermined value, the induction motor rotates, and in the first state in which the rotation speed of the induction motor is constant, the slip frequency signal is slightly changed, In the second state in which the voltage command signal changes due to the change in the slip frequency signal and the rotation speed of the induction motor becomes constant again, the voltage command signal in the first state and the voltage command signal in the second state are compared. Then, the slip frequency signal is slightly changed again according to the result, and the voltage command signal changes due to the change of the slip frequency signal. In the third state in which the rotation speed of the induction motor is constant, the voltage command signal in the second state is compared with the voltage command signal in the third state, and the slip frequency signal is slightly changed again according to the result. A motor control device characterized in that the slip frequency signal is changed in the same manner as described above according to the voltage command signal. 2. The slip frequency generating means outputs the slip frequency signal in response to the voltage command signal, whereas the output frequency range of the slip frequency signal is limited. Motor control device.