Permanent magnet motor capable of changing the number of poles by a factor of three

To reduce energy consumption, we developed a technique that rapidly varies the number of magnetic poles in a permanent-magnet (PM) motor. In this paper, we propose a novel PM motor that can change the number of magnetic poles by a factor of three. The motor has a rotor embedded with PMs that have both high and low coercive forces. When the motor operates with 6 poles, it produces a PM torque at low speed. If the motor changes to 2 poles at a high speed, the field due to the d-axis current reverses only two PMs with low coercive force. We describe the principle and basic characteristics of the motor. The results of our analysis show that the proposed motor can vary the induced voltage from 39% to 100% and reduce the core loss by about 40%.