An Improved Low-Noise Sensorless PMSM Drive able to Face Highly Intermittent Load Torque

Sensorless algorithms for Permanent Magnet Synchronous Motor (PMSM) are generally divided in methods for the low speed region and methods for the medium-high speed region. Algorithms based on high frequency injection show a good behavior for low motor speed, nevertheless voltage injection is associated to loud acoustic noise and additional losses. On the contrary, methods based on back-electromotive force and on rotor flux observer are passive methods (i.e. they do not require additional voltage injection); however they guarantees high performance only in the medium-high speed region. In this paper, rotor flux observer based sensorless algorithm performance is analyzed, specially focusing on behavior at low speed. No-load, linear torque, quadratic torque and compressor-type torque load is experimentally tested.