Electromagnetic Performance Improvement Of Salient Pole Synchronous Motor With Improved Rotor

The wound field synchronous motor(WFSM)has the advantages of adjustable excitation field and strong flux weakening and speed expansion ablity.What’s more,there is no need rare eath materials in WFSM.Therefore,more and more experts and scholars pay more attention to the development of WFSM.The torque density of traditional electrically WFSM is relatively low,so its application in electric vehicles and other fields is limited.Therefore,this thesis improves the torque density and electromagnetic characteristics of WFSM by improving the rotor structure of WFSM with salient pole,enhancing the competitiveness of WFSM in the field of electric drive.This thesis gives the theoretical analysis and completes the simulation verification according to the above research contents.Firstly,the mathematical model of WFSM in dq axis coordinate system is constructed,and the electromagnetic design of WFSM is carried out according to the design index.On the basis of the design results,the finite element calculation model of WFSM is established in Maxwell software,and the electromagnetic characteristics under the situation of no-load and load are simulated and analyzed to verify the electromagnetic design results.Based on the analysis of magnetic characteristics of dq circuit,the design of rotor with flux barrier is carried out.The mechanism of improving reluctance torque by setting flux barrier is analyzed,and the design principles and methods of flux barrier under the conditions of keeping the width of pole body unchanged and the width of d-axis magnetic circuit unchanged is discussed.The results show that when the width of d-axis magnetic circuit remains unchanged,the total width of double flux barrier accounts for about 7.8% of the rotor pole width and the distance between flux barriers accounts for about 5.7% of the rotor pole width,the total torque increases from 5.72 N.m to 6.10 N.m.,increased by 6.6%.Using the response surface method(RSM)of design of experiment(DOE),the optimization design is carried out with the magnetic barrier width,the magnetic barrier top position,the rotor eccentricity and the magnetic barrier centerline position as variables and the output torque and torque ripple as the optimization objectives.The simulation results show that the torque ripple of the optimized motor is reduced by 14%,but the total torque also decreases slightly.In addition,the stress analysis and stress calculation of the magnetic barrier rotor are carried out.The simulation results show that the centrifugal force borne by the rotor under rated condition will not affect the structural stability of the motor.The utilization of reluctance torque is discussed to improve by setting permanent magnet in the flux barrier to produce the magnetic bias effect,which reduces the current angle difference corresponding to the maximum excitation torque and maximum reluctance torque and further improve the total torque.The maximum total torque increases from 6.10 N.m to 6.93 N.m.Compared with that of only setting flux barrier,it is increased by 13.6%.In addition,the research results show that the method of increasing the utilization of the reluctance torque is more suitable for light load conditions considering the saturation characteristics of magnetic circuit.At this time,the efficiency of the motor is improved by about 2% compared with the original model.