Low-speed Control Device of Three-phase AC Asynchronous Motor

Abstract

The invention discloses a low-speed control device for a three-phase alternating-current asynchronous motor. The low-speed control device comprises a main circuit, a detection circuit, a control circuit and a driving circuit which are connected in sequence, wherein the control circuit comprises a rotating speed ring module, a current ring module and a pulse width control signal generating module, the rotating speed ring module is used for receiving the given rotating speed and feedback rotating speed of a rotating speed ring, calculating the given value of a current ring and outputting to the current ring; the current ring module is used for receiving the output value of the rotating speed ring and the feedback value of the current ring, and outputting the output value of the current ring; the pulse width signal generating module is used for receiving the output value of the current ring, generating a pulse width control signal for controlling the three-phase alternating-current asynchronous motor, and transmitting the pulse width control signal to the driving circuit to control the three-phase alternating-current asynchronous motor to run stably in a low-speed state. According to the low-speed control device, the problems of high pulse and high noise of the motor during low-speed running can be restrained, and the working efficiency of the motor is increased.

Description

technical field [0001] The invention relates to the field of motor control devices, in particular to a low-speed control device for a three-phase AC asynchronous motor. Background technique [0002] With the rapid development of industrial production, the application of AC asynchronous motors is becoming more and more extensive. More than 70% of the electric energy in daily life is used for the control of AC asynchronous motors. Therefore, it is very necessary to study high-performance motor control technology to reduce operating loss and prolong motor life while meeting the requirements of operation, technology, and production. [0003] During the working process of the AC motor, its speed is related to the frequency of the power supply. In order to make the motor run stably, a frequency converter is usually used to change the frequency of the AC power, so as to achieve the purpose of changing the speed of the motor. When the motor is running at a low speed, the AC speed c...

AI Technical Summary

Problems solved by technology

When the motor is running at a low speed, the AC speed control system composed of a frequency converter has a small starting torque when starting at a low speed, making it difficult or even impossible to start the AC motor; due to the high-order harmonics generated during the operation of the frequency converter, Cause the speed pulsation of the motor and the heating of the motor, and the noise of the motor will also increase. When the distance between the frequency converter and the motor is large and the high-order harmonics interfere with the control circuit, it is easy to cause the pulsation of the motor speed; when the AC motor is low-speed and stable When running in the normal state, due to the fluctuation of the grid voltage or the change of the system load and the distortion of the output voltage waveform of the frequency converter, the vibration of the motor will be caused.

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