Effects of pole changing in a permanent magnet motor

To reduce energy consumption, we developed a technique that varies the number of magnetic poles in a permanent magnet (PM) motor. We propose a PM motor that can change the number of magnetic poles and produce two types of torque. When the motor operates with 8 poles, it produces a PM torque at low speeds. When the motor changes to 4 poles, it produces both PM torque and reluctance torque at high speeds. We explain the principle and basic characteristics of the motor, which has a PM magnetized by the pulse d-axis current of the armature winding. The results of our experiment show that the proposed motor reduces core loss by 49% or 33% and triples the speed range of the motor.