Design of high torque density multi-core concentrated flux-type synchronous motors considering vibration characteristic

Conventional mechanical and hydraulic systems have been rapidly replaced by electromechanical systems. The demand for electric motors has significantly increased for automotive parts. Nowadays, there are various types of permanent magnet synchronous motors (PMSMs) applied to automotive chassis applications such as steering systems, electric boosters, electromechanical brakes, and more. The electric motors for chassis components are mainly designed by surface mounted PMSMs (SPMSMs) because they have a relatively simple rotor structure. However, the SPMSM has a low torque density because its magnetic airgap becomes longer by installing the retainer for structural stability. In order to overcome such limitations of the SPMSM, various types of interior permanent magnet synchronous motors (IPMSMs) have been developed. In the mass production, nevertheless, the small sized IPMSM has significant leakage flux in the bridge of the rotor core because the thickness of the bridge is limited by the molding technology and structural safety. In order to reduce this leakage flux and increase the torque density, the design for a new rotor structure is needed. In this paper, a multi-core concentrated flux-type synchronous motor is proposed and designed for electric booster application. Then, the performance of the designed motor is analyzed by a finite element analysis.