Advantages of IPMSM with adjustable PM armature flux linkage in efficiency improvement and operating range extension

Because of the many advantages of the interior permanent magnet synchronous motor (IPMSM) over the induction motor, it has been used in many industrial applications as well as office and home equipment. Besides high efficiency, extensive constant power operating range is also desired in many applications. This paper presents a novel method to further extend the operating range and improve efficiency of the IPMSM. An IPMSM with adjustable PM armature flux linkage by means of adapting flux-shortening iron plates at both sides of the rotor is introduced. FEM analysis and experiments show that the permanent magnet armature flux linkage can be effectively adjusted by controlling the gap length between iron plates and the rotor. It is verified that the operating range of the proposed IPMSM can be greatly extended by lowering the PM armature flux level above base speed using the iron plates. The lowered permanent magnet armature flux linkage allows the proposed IPMSM to draw less d-axis armature current in the operating region of flux-weakening control. As a consequence, efficiency of the proposed IPMSM as well as power factor can be significantly improved, especially at light load and high-speed operation condition. The performance of the proposed IPMSM is verified with experiments on a test motor