A Novel Control Method for Rotor Eddy Current Loss Reduction of High-Speed Permanent Magnet Brushless DC Motors

High-speed brushless dc motor (BLDCM) has been widely used in many applications, but the rotor eddy current loss has always been a key constraint by traditional PWM control methods because of the serious distortion of stator current. Although this loss is only a small portion in the overall power loss, it still may expose the magnets to high risk of overheating and demagnetization, especially for the inner-rotor motors with weak cooling condition and motors operated at high-speed region. This paper presents a novel control method, asymmetrical dual-pulse (ASDP) variable conduction period control method, for high-speed permanent magnet BLDC motors to reduce the rotor eddy current loss. Comparative studies of stator current waveforms, harmonic components, and rotor eddy current loss have been carried out between the ASDP method and several traditional control methods. The FEM simulation and THD analysis results confirm that the ASDP method can effectively eliminate the even harmonic and weaken the odd harmonic components in stator current, so that the rotor eddy current loss can be significantly reduced.