Sensorless Self-Recognition Research for the Speed of Magnetic Suspension Compressor

The speed of the Magnetic suspension compressor is very important for the control of the entire compressor. In general, no additional speed sensor is arranged in the compressor. During the operation of the compressor, the speed of the motor can be estimated by designing an observer for the motor current, voltage and other signals. However, when the motor idles in inertia during shutdown, the current of the motor cannot be obtained by the observer. This article introduces a speed identification method based on phase-locked loop in the idle state of the motor, which can accurately obtain the rotational speed of the motor in the idle state, and provides a solid guarantee for the unbalance compensation of the magnetic bearing in the whole process. The bearings can be stopped in time when the machine stops, making the shutdown process more intelligent.