Determination of Differential Inductances for a Permanent Magnet assisted Synchronous Reluctance Machine with a Ribless Rotor

摘要

In the last decade permanent magnet assisted synchronous reluctance machines (PMaSynRM) have gained more interest. Compared to induction machines in industrial applications, a good efficiency is achieved due to low rotor losses. The low power factor of a pure synchronous reluctance machine is mitigated by assisting ferrite magnets. These magnets are environmentally friendly, cost-saving and do not suffer under strong price fluctuations. As a drawback, they offer a low energy density compared to rare-earth magnets. The considered machine includes a special ribless rotor which provides a high anisotropy and low cross-coupling over the whole current operating area. Hence, the machine is well suited for sensorless operation. Furthermore, a high anisotropy has a positive impact on the torque. Differential inductances have a strong influence on the current waveform and on the sensorless control capability at low or zero speed. Therefore, the differential inductances are evaluated via three approaches: Finite Element Analysis, the flux linkages and test signal injection.