A Novel High Torque Density Dual Three-Phase PMSM With Low Space Harmonic Content

A novel 36-slot/14-pole dual three-phase permanent magnet synchronous machine (PMSM) is proposed to suppress non-working space harmonics in the synthesized magnetomotive force (MMF) and improve torque density simultaneously. The machine adopts unequal coil-turns winding and special stator core which includes two different types of slots, namely double-layer slots (DLSs) and single-layer slots (SLSs). The special structure of the machine improves the working space harmonic and eliminates lower non-working space harmonics in MMF, which leads to torque promotion and permanent magnet (PM) loss reduction. Harmonic content in MMF of the proposed machine is derived from theoretical analysis and verified by finite element (FE) calculation. Besides, the proposed machine is compared with existing machines, from aspects of MMF, back electromotive force (EMF), torque, losses, efficiency, unbalanced magnetic force (UMF), and torque-speed characteristic. The proposed machine has higher torque density, higher efficiency, and lower PM loss than existing machines.