A novel wheel hub motor based on U-shaped electromagnet working principle and torque characteristics

The development of electric vehicles has brought about a campaign for researching and developing new electric motors. In this paper, a novel wheel hub motor is proposed, according to the regulation that electromagnet and permanent magnet interact in the way that homopolar magnets repel and heteropolar magnets attract. The motor can be assembled by identical electromagnetic units with U-shaped electromagnets in the stator and permanent magnets in the rotor, making it convenient and flexible for practical requirement. The voltage equation and the formula of electromagnetic torque are given by analyzing electromechanical energy conversion relationship, which is verified by simulation with finite element method. With the total torque decomposed into three components, the research emphasis of this paper is placed on torque characteristics, including torque ripple, average torque, torque per ampere and the ratio of torque to copper loss as the current varies, which is significant for the optimal design and speed regulation of this type of motors.