Design And Analysis Of A Stator Separated Magnetic-field Modulated Motor

In the conventional low-speed high-torque industrial occasions,the mechanical gears are employed to decrease the motor speed to realize low speed operation.However,the employment of mechanical gears will deteriorate the energy conversion efficiency of the system.In order to solve this problem,the direct drive technology is emerged and rapidly developed.In the direct drive system,it is necessary to apply the motor,which has low-speed high torque character inherently.However,the demand for torque density in direct drive system is continually higher,the torque density of the permanent magnet motor is finite and it gradually cannot meet the torque requirement of the direct drive system.Based on the conventional permanent magnet motor,the magnetic-field modulated motor is proposed by employing the magnetic-field modulation effects,which can effectively improve the torque density.However in the stator permanent magnet magnetic-field modulated motor,there exists a problem that the windings and permanent magnets in the stator will contend for the limited stator space,which will make it difficult to further improve the torque density.The stator of the stator permanent magnet magnetic-field modulated motor is artfully separated and the stator separated magnetic-field modulated motor is proposed,whose windings and permanent magnets are placed at outer and inner stator,respectively.Therefore,the proposed motor can effectively solve the space conflict problem.The contents of this paper are summarized as follows:1.The similar and different structure characters of the stator permanent magnet and stator separated magnetic-field modulated motors are investigated.Based on the flux density of modulated permanent magnet magnetic field and winding magnetomotive force,the operation principle of the stator permanent magnet magnetic-field modulated motor is theoretically analyzed.In addition,considering the different air-gap flux density components,the operation principle of the stator separated magnetic-field modulated motor is investigated and verified.2.The outer stator diameter,stack length,magnetic gear ratio and winding connection type are determined based on the motor design target.Furthermore,the magnetic gear ratio effects on the motor performances are highlighted and the optimized magnetic gear ratio is designed.In order to obtain the optimized torque performance,the parameters of the proposed stator separated magnetic-field modulated motor are optimized for maximum torque.The proposed motor,which can exhibit high torque and simultaneously reduce the permanent magnet irreversible demagnetization risk,is successfully designed.3.The electromagnetic performances,including the back-EMF,torque performances and losses of the proposed separated stator magnetic-field modulated motor,stator permanent magnet magnetic-field modulated motor and the conventional permanent magnet motor are comparatively simulated.In addition,based on the stagger angle between the inner and outer stator,the mechanism that the torque ripple can be reduced by stator separation is theoretically investigated.4.The prototype manufacture scheme of the proposed stator separated magnetic-field modulated motor is formulated and the manufacture process is illustrated.Moreover,the feasibility research on rotor fixed mode is carried out.The experimental platform is constructed and the prototype is tested in order to verify the simulation analysis of the electromagnetic performances.