Investigation of Flux-Barrier Design Principle of PM-Assisted Synchronous Reluctance Machines Used for Electric Vehicles

Permanent magnet assisted synchronous reluctance machines (PMa-SynRMs), which adopt the multilayer flux-barrier (FB) structure to increase the reluctance torque, are increasingly used in electric vehicles (EVs) due to their characteristics of excellent electromagnetic performance. However, the effect of key FB structural parameters including FB layer number and thickness on reluctance torque still lacks theoretical support at present. In this article, first the dq-axis flux versus FB layer number and thickness is theoretically derived based on the equivalent magnetic circuit (EMC) model and verified by finite element analysis (FEA). Second, the influences of FB layer number on dq-axis inductance and reluctance torque under different currents are investigated. After that, the relationship between electromagnetic torque and current angle of PMa-SynRMs adopting different FB layer numbers is also studied. Finally, a PMa-SynRM adopting the rotor structure of three FB layers is designed and manufactured based on the theoretical analysis result. The relevant experimental research of prototype is conducted and the experimental results are in good agreement with the simulation.