RESEARCH ON HIGH EFFICIENCY INTERIOR PERMANENT MAGNET SYNCHRONOUS MOTOR WITH ADJUSTABLE PM ARMATURE FLUX LINKAGE

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With the rapid development of power electronic devices, rare earth permanent magnet (PM) and motor control technology, interior permanent magnet synchronous motor (IPMSM) is being widely used in various applications. In some applications such as electric vehicles and compressors, except for high efficiency, extensive constant-power operating range is also desired. Several novel rotor structures are studied to further extend operating range and improve efficiency of IPMSM. IPMSM with adjustable PM armature flux linkage by adapting flux-shortening iron plates at both sides of rotor or iron pieces in the space of flux barriers is suggested. FEM analysis and experiments show that the PM armature flux linkage can be effectively adjusted by using these methods. 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. The lowered PM armature flux linkage allows the proposed IPMSM to draw less d-axis armature current in the 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. The variations of efficiency relating to operating conditions and PM flux level are discussed. The efficiency and power factor maps show that the high efficiency and high-power factor operating area of the proposed IPMSM is much larger than that of the conventional one, indicating the advantage in improving efficiency. Based on the analysis of efficiency performance at various decreasing rates of PM armature flux linkage, optimal decreasing pattern of PM armature flux linkage is obtained corresponding to various operating conditions. Investigation is also done to simplify the driven pattern of iron plates and iron pieces. The performances of the proposed IPMSMs are verified with experiments on several testing motors.