Electromagnetic Performance Analysis of a Field-Modulated Permanent Magnet Motor Using Improved Hybrid Subdomain Method

The hybrid subdomain method (HSDM) combining conventional SDM with equivalent magnetic network has been proved to be a qualified approach to field prediction. However, this method still suffers two issues: first, the saturation effect of stator core is considered but that of rotor core is ignored, thus causing no-accuracy calculation; second, the mathematical complexity is inevitable due to adoption of virtual line-current density as extra interface conditions. This work is to develop an improved HSDM (IHSDM) for accurately and efficiently predicting the electromagnetic performance of a field-modulated permanent-magnet motor. The key of the proposed IHSDM is to fully consider magnetic saturation inside both stator and rotor cores. More importantly, the replacement of virtual-line current density by virtual-surface magnetization and current density makes interface conditions as simple as the SDM. The quantitative comparisons with conventional HSDM and FEA are conducted and the prototyping tests are also performed. It shows that the proposed IHSDM has lower time consumption and occupied memory, and electromagnetic quantities have about two times more accuracy than conventional HSDM. Additionally, a dynamic calculation is achieved by the IHSDM and verified by FEA.