PM Eddy Current Loss Analysis and Suppression in a Spoke-Type Flux-Modulation Machine With Magnetic Flux Barrier Design

This paper investigates the permanent-magnet (PM) eddy current (EC) loss in a spoke-type flux-modulation (STFM) machine with inverted T-shaped permanent magnets. The key is to design appropriate flux barriers in such rotor structures to suppress the PM EC loss with little effect on torque performance. First, the main harmonic orders generating PM EC loss are analyzed based on the air-gap magnetic field modulation. The findings indicate that some non-working harmonics produce PM EC loss, which can be suppressed by reducing these harmonics. And the proportion of PM EC loss produced by these harmonics is calculated through the analysis of a three-dimensional model of PM EC loss. Then, a new rotor structure with flux barriers is proposed to suppress PM EC loss based on ensuring the torque performance by reducing the 1st-order harmonic. Finally, the electromagnetic performance of the two machines is compared by finite element analysis. Stress analysis and temperature distribution simulation are also carried out to prove the feasibility of this structure. The results show that the proposed structure is effective in suppressing PM EC loss with little influence on the main electromagnetic performance.