Ultra-High-Speed Motor Design to Reduce Inductance Voltage Drop through Permanent Magnet Overhang Structure

Abstract

Since the motor is driven by an inverter, it is essential to design the motor in consideration of electrical specifications. The DC link voltage limits the fundamental armature voltage of the motor. Ultra-high-speed motors have large voltage drop due to inductance. In order to satisfy the voltage-limit condition, a permanent magnet (PM) overhang structure can be considered to reduce the inductance voltage drop. Since back-electromotive force (EMF) increases when the PM overhang structure is applied, the stack length may be reduced at the same level as back-EMF. Accordingly, the inductance voltage drop is reduced due to the reduction of the stack length. In particular, since surfaced-mounted synchronous motor (SPMSM) does not generate reluctance torque, the same output torque can be maintained even when the inductance is reduced through a PM overhang structure. The PM overhang factor is used to reduce the computation time by reflecting the effect of the PM overhang structure in the 2-dimensional finite element analysis. Accordingly, the distributed winding SPMSM is designed to reduce the inductance by reflecting the PM overhang factor.