Study of An Improved Biased Flux Intermodular Permanent Magnet Motor

This paper proposes an improved biased-flux motor in which the permanent magnets (PMs) are placed between the stator modules, therefore called intermodular PM (IMPM) motor. The proposed structure has increased the torque density while maintaining a low torque ripple. Moreover, due to the specific placement of PMs, the PMs are extensively protected from demagnetization. The operation principle of the proposed IMPM motor is thoroughly discussed using flux modulation theory and is comparatively analysed with other biased-flux structures. Based on this analysis, a new theoretical formulation is also drawn to calculate the power factor, which involves design related parameters. It has been studied that since the PMs are far from armature winding in the proposed structure, the PMs’ thermal stress is even less than other stator-PM structures. Due to this placement, the power factor of the proposed motor is drastically improved compared to other biased-flux motors. The no-load and full-load performances of the IMPM motor are studied using the finite element method (FEM). A comprehensive comparative study is also conducted to better locate the proposed structure in the biased-flux motors. Finally, a 6/11 IMPM motor is prototyped and tested to experimentally validate the theoretical and FEM analyses.