Examination of the Stability of Sensorless Control of Permanent Magnet Synchronous Motor in the case of fluctuating load

The motor is desirable high efficiency, because it is consuming about 50% electrical energy. Therefore, Permanent Magnet Synchronous Motor (PMSM) is gathering attention and being widely applied. The vector control of PMSM must have information of magnet pole position. So, it is necessary to attach position sensor. However, several problems occurs by attaching a position sensor. For example that degradation of reliability, adaptability of the environment is reduced, and cost is high. These problems should be solved. Thus, vector control without a position sensor has attracted attention. A compressor is a load of fluctuation torque because it repeats suction and compression of refrigerant gas. When such load is applied to the sensorless control, it becomes unstable. In this paper, the effect of torque fluctuation is checking when the compressor is moved by sensorless control of PMSM.