Comparison between Surface-mounted and Interior Permanent Magnet Synchronous Machines for Low Voltage Regulation Applications

In this paper, the surface-mounted permanent magnet (SPM) and interior permanent magnet (IPM) machines are designed and compared for low voltage regulation applications. The principles of low voltage regulation designs in SPM and IPM machines are explained. Then, a SPM machine using halbach-array PMs and an IPM machine with U+V rotor topology are designed and optimized using the same stator and air-gap length to achieve similar rated voltage and power and voltage regulation rate. The performance between optimized SPM and IPM machines are analyzed and compared by using finite element (FE) analysis. It is found that the SPM machine can achieve higher torque density with smaller PM usage, while the IPM design can significantly improve efficiency by reducing PM loss and can ease manufacturing complexity and cost in particular for halbach-array PMs.