Design of Concentrated Flux Synchronous Motor with Ferrite Magnet Considering Mechanical Stress at High Speed

This paper proposes a design of 90 kW concentrated flux synchronous motor (CFSM). A ferrite magnet is used because of low price compared to rare-earth materials and this spoke type structure of motor can be an alternative to the interior permanent magnet synchronous motor (IPMSM) using NdFeB. However, a greater size of ferrite magnet is required to achieve the same torque as NdFeB is used, because the residual induction of ferrite is approximately one third of NdFeB. Consequently, the spoke type structure is applied to improve the torque density. In the design process, methods of deciding the stack length, stator diameter, rotor diameter, and the number of poles and slots are suggested. Series turns per phase are determined by applying back-electromotive force-inductance map (EL map) in the initial design. A response surface method is applied for the optimization. Furthermore, a structural analysis is also conducted to confirm the safety at high speed. Finally, test of CFSM is conducted for the verification.