Radial Force Characteristics of a Consequent-Pole Permanent Magnet Synchronous Motor

Consequent-pole Permanent Magnet Synchronous Motors (CPPMSMs) have only half the number of permanent magnet (PM) of Permanent Magnet Synchronous Motors (PMSMs), which can significantly reduce the usage of PM. In previous papers, how the permanent magnet pole and core pole affect the torque characteristics of the motor has been analyzed, but how they affect the radial electromagnetic force of the motor has not been studied comprehensively. Firstly, based on the principle of magnetic field modulation, the influence of rotor structure on the armature reaction magnetic field and the influence of stator teeth on the permanent magnet magnetic field are analyzed. Secondly, based on the Maxwell stress tensor method, the characteristics of the radial electromagnetic force of CPPMSMs are studied in detail. Some exciting phenomena are found: When the polar logarithm of CPPMSM is an integer multiple of the greatest common divisor of the number of slots and poles, the minimum order of the radial electromagnetic force of CPPMSM is the same as that of PMSM, but the radial electromagnetic forces with more frequency are added; when the polar logarithm of CPPMSM is a fractional multiple of the greatest common divisor of the number of slots and poles, the minimum order of radial electromagnetic force of CPPMSM is lower than that of PMSM, and more radial electromagnetic forces with multiple frequencies are added. Then, the consistency of the characteristics of radial electromagnetic force and vibration is verified, through the vibration simulation of the motor. Finally, the accuracy of the analysis results is further confirmed by the vibration test of the prototype.