Design And Optimization Of High Speed Permanent Magnet Assisted Synchronous Reluctance Motor

There are many advantages of high-speed motors,such as: higher power density,smaller size,smaller material consumption,lower cost,being directly connected to the load,no intermediate variable speed device,less noise,and higher efficiency of the drive system.Therefore,high-speed motors have been widely used in both military and civilian fields.Due to the limitation of mechanical strength of rotor materials,surface mounted rotor structure is applied to most high-speed motors with the sleeve being used to protect the rotor,while the research on interior rotor structure of highspeed motors is relatively few.In the design process of high-speed motors,many key issues need to be analyzed and studied,including the electromagnetic design of the motor,the strength analysis during the high speed rotation of the rotor,the calculation of the loss of the motor’s each part,the design of the cooling structure of the motor and the temperature rise analysis.In this paper,two high-speed permanent magnet assisted synchronous reluctance motors with different rotor structures are designed,the rated power of 7.5 k W and the rated speed of 18000 r/min.Detailed research and analysis are carried out.The main research content of the paper can be divided into the following five parts:1.Combined with the rated data and performance indicators of the motor,the initial models of the two rotor structures are designed as UI-type rotor structure motor model and VV-type rotor structure motor model,including the design of stator,winding,rotor,permanent magnet and rotor shaft and so on.After that,the two motor models are simulated and analyzed by Ansoft software,and then the no-load simulation results and load simulation results of the two motor models are analyzed and compared to prove that the design of the two motor models is reasonable.2.The stress distribution of the two rotor structures in the process of high-speed rotation is simulated by the structural statics module of ANSYS Workbench to obtain the stress distribution of the two rotor structures.Then the influence of the rotor rotation speed on the rotor’s maximum equivalent force is analyzed.3.The multi-objective optimization of the two motor models is carried out by using the genetic algorithm NSGA-Ⅱ,using torque pulsation,cogging torque and rotor equivalent force as the optimization objectives of the motor.Besides,to ensure the rationality of the optimized two motor models,their simulation analysis is done through the finite element software.Then,the changes in motor performance parameters between before and after the optimization to ensure the effectiveness of multi-objective optimization of the two motor models.4.The stator core loss of the two motor models are simulated and calculated respectively by Ansoft software and the winding copper loss of the motor is calculated by the analytical method of equations.Besides,the calculation model of the wind friction loss on the outer surface of the rotor is built in ANSYS Workbench software,and the wind friction loss on the outer surface of the rotor is simulated and calculated by using its fluid analysis module to obtain the wind friction loss of the motor and further analyze the three main factors affecting the wind friction loss on the outer surface of the rotor,which includes the inlet wind speed in the fluid region,the roughness of the outer surface of the rotor and the rotor speed.5.The spiral water-cooling structure is used to cool the designed motors,and the temperature rise simulation model of the two motors is established.The temperature rise of the two motor models is simulated by the fluid simulation module in ANSYS Workbench software to obtain the temperature rise results of each part of the two motor models.Besides,the influence of the spiral water channel’s cooling water velocity on the temperature rise of the motor is studied and analyzed.