Design and optimization of an interior permanent magnet machine with asymmetric stator iron yoke applied in rail transportation

摘要

An interior permanent magnet (IPM) machine applied in rail transportation is designed and optimized in this paper. A quasi-octagonal stator iron yoke is adopted in the machine in order to meet the requirement of the installation while the parallel slot structure is also employed due to the arrangement of the performed windings. The method of equivalent stator slot is proposed in this paper to analyze the effects of asymmetric stator iron yoke (ASIY) and to explain the low order harmonics introduced by the ASIY. Without slot or pole skew, the total harmonic distortion (THD) of the back electric motive force (EMF) of the IPM machine is optimized to lower than 3% and the peak-to-peak torque ripple of the machine at rated speed is lower than 5%. Moreover, some key parameters such as the stator slot number, stator inner radius and rotor types, which have remarkable influences to the machine performance, are also discussed in this paper. The performance of the machine is verified by the finite element method (FEM) and the prototype is under built.