Basic principle and maximum torque characteristics of a six-phase pole change induction motor for electric vehicles

In addition to basic characteristics such as small size, lightweight and easy maintenance, the electric vehicle (EV) motor is required to possess characteristics that allow for the production of high torque in low-speed region and to realize a wide-speed range of constant power in high-speed region. In an attempt to improve further the constant power operation of the induction motor (IM), this paper proposes a six-phase pole change IM (six-phase PCIM). The six-phase PCIM further expands the constant power operation range without increasing either volume or current of IM. To clarify the basic principle and torque characteristics of the six-phase PCIM, its winding method and distribution of magnetomotive force (mmf) will first be examined. Then, by establishing a performance calculation method based on a quasisinusoidal wave method, the feasibility of a highly precise performance calculation sufficient for actual use will be demonstrated. Furthermore, by clarifying through experiment the maximum torque characteristics, the feasibility of expansion of the constant power operation range will be confirmed and its effectiveness in the EV will be discussed.