Design and analysis of variable flux pole-changing permanent magnet memory machine

Pole-changing permanent magnet (PM) machines, which can offer wide operating speed range, have attracted global attention in industry application. However, the previous pole-changing PM machines adopting distributed winding, suffer from lengthy end winding and relatively low efficiency. Therefore, this paper presents a new variable flux pole-changing PM memory machine (VF-PCPMMM) employing fractional slot concentrated winding, which can increase utilization ratio of winding and suppress cogging torque regardless of the different pole modes. The pole number of rotor can be changed, when the magnetization directions of variable flux PMs are varied by applying current pulses with different directions in the stator winding. Besides, the air gap flux density can be flexibly adjusted by regulating the magnitudes of the current pulses. The topology and design principle of VF-PCPMMM are described in detail, and the field regulation characteristics in different pole modes are analyzed by using finite element method (FEM). Besides, the torque characteristics are comprehensively investigated under different magnetized levels of AlNiCo PMs.