Inductance characteristics of PMSMs and their impact on saliency-based sensorless control

Advantages of operating a Permanent Magnet Synchronous Machine (PMSM) without a position sensor are many and are well known. This paper presents a study of the effects of space harmonics in the incremental inductances and their impact on the machine saliency. The effects of space harmonics exclusively due to the machine (i.e., the saturation saliency distribution) are given particular consideration. The results are illustrated through inductance analysis and measurement of inductance profiles of two similar PMSM machines. The space harmonics in the inductance profiles are correlated with the position estimate distortions through a Matlab/Simulink embedding finite element (FE) machine simulation. Significant differences in sensorless operation of the two machines are found which correlate to the inductance profiles. This illustrates that inductance profiling can inform upon machine design in order to improve sensorless capabilities.