Analysis Of Air-Gap Magnetic Field Modulation In Reluctance Machine

As the core of driving electric vehicle,the electric motor affects the operation of electric vehicle significantly,which is widely concerned by the scholars at home and abroad.Since the reluctance motor has no permanent magnet and excitation windings,it has become the research hotspot in the electrical vehicle industry with the advantages of low cost,solid structure,wide speed range and high temperature non demagnetization performance.Up to now,the research of reluctance motor is mainly focused on the design of new structure and optimization to analyze the torque performance.Based on the mechanism of magnetic field modulation,this paper analyzes the process of the reluctance motor air gap magnetic field modulation in the perspective of the rotor pole and winding structure.By analyzing the harmonic order due to modulation,the effective working harmonic order and its torque contribution are obtained.Finally,an excellent torque performance reluctance motor is designed and manufactured,which lays a solid experimental foundation for further research on reluctance motor.The main academic research achievements of this paper are contained as follows:1.The traditional analysis method of the magnetic gear motor magnetic field modulation is combined with the universal air gap magnetic field modulation theory called "three-factor" method.This method described the modulation process of the reluctance motor initial magnetomotive force modulated by the salient pole modulator and the armature winding.The air gap magnetic field modulation mechanism of the reluctance motor salient stator and rotor is analyzed and verified by finite element simulation.2.The air gap permeance model is built to derive the air-gap flux density expression under the modulation of stator teeth and double modulation of rotor teeth.The air gap magnetic density harmonic order and rotation speed in two magnetic fields are obtained respectively,which lays a theoretical foundation for the research on reluctance torque.3.The mechanism of reluctance torque generation is analyzed by Maxwell stress tensor method and the effective working harmonic order generating reluctance torque is determined by magnetic field superposition.On the basis,the torque generated by the effective working harmonic order can be calculated specifically.In-depth study on the method of weakening or enhancing the specific harmonic order air gap magnetic density amplitude,which provides reference for manufacturing a reluctance motor with better torque performance.4.The modulation process of the reluctance motor with different winding structure is analyzed by magnetic field modulation theory.Five typical winding connections are chosen to analyze the expression of air gap magnetic density of their corresponding stator magnetomotive forces under the same salient pole stator and rotor.The effective harmonic order and torque contribution is analyzed based on Maxwell stress tensor method.5.This paper systematically analyzes and designs a reluctance motor,and the electromagnetic performances are verified by finite element method(FEM)The simulation results agree well with the theoretical analysis ones.