Performance of induction motor with free-rotating magnets inside its rotor

This paper presents a new induction motor that has free-rotating magnets inside a rotor. The magnets can revolve freely against the rotor with the shaft. In this motor, the airgap flux is provided by both rotating permanent magnets and the stator coil current. A prototype motor was fabricated by modifying the rotor of a conventional three-phase four-pole 400 W squirrel-cage induction motor. The experimental results of a prototype motor showed superior performance in comparison to conventional motors in terms of the power factor, efficiency and torque characteristics. The power factor can be controlled to be unity, leading or lagging by changing the supply frequency and/or source voltage. The efficiency of the motor, over a wide output power range, is remarkably higher than that of the same size conventional induction motor. A high torque can be obtained in a high speed area