High-Efficiency Drive Method of Adjustable Field IPMSM Utilizing Magnetic Saturation

This paper describes a high-efficiency drive method of an adjustable field Interior Permanent Magnet Synchronous Motor (IPMSM) utilizing magnetic saturation. The adjustable field IPMSM can control the magnetic field flux using magnetic saturation caused by a modulation current. In general, it is said that motor efficiency is high at operating points where the copper loss and the iron loss are balanced. However, the high-efficiency drive range of a conventional PMSM is narrow because the magnetic field of the PMSM is constant. On the other hand, it is possible in the proposed adjustable field IPMSM to expand the high-efficiency drive range because the field amount can freely be adjusted by the modulation current. Therefore, this paper examines an optimal modulation current for a high-efficiency operation. To derive the optimal modulation current, losses and efficiency of the proposed adjustable field IPMSM are formulated based on the measured motor parameters. In addition, it is confirmed from several experimental tests that the high-efficiency driving range can be expanded due to the optimal modulation current.