Reduction of Magnetization Current in a Variable-magnetization Internal Permanent Magnet Motor with Two U-shaped Arrangements for Electric Vehicles

Abstract

We developed a variable-magnetization internal permanent magnet (VM-IPM) motor for electric vehicles (EVs). This motor can vary the magnetization of a permanent magnet (PM) to realize highly efficient operation across a wide range of speed. Optimizing the inverter capacity is crucial for maintaining quality and reliability during the mass production of traction motor systems for EVs. However, the magnetization current should be less than thrice the rated current if the magnetization state of the PM is to be varied without increasing inverter capacity. Our proposed VM-IPM motor can vary even small magnetization currents. Our results confirm that the proposed motors in which variable permanent magnets (V-PMs) and constant permanent magnets (C-PMs) are arranged inside two U-shaped cavities provide excellent operation performance over a wide range of speed and power. In addition, the proposed motors can vary the magnetization state of the PMs by applying demagnetization and remagnetization currents that are twice the rated current. The back-electromotive force of the motor can vary from 56.4% to 97.4% and from 61.2% to 93.4% in the parallel and series models, respectively, because of the varying magnetization state of the V-PMs at a magnetization current that is twice the rated current.