Design Method And Efficiency Analysis Of Hairpin Winding Permanent Magnet Motor For Electric Vehicles

New energy electric vehicles have received widespread attention due to their energy-saving,environmentally friendly,and efficient characteristics.The driving motor is the core component of electric vehicles,and its output characteristics are directly related to the economic and dynamic performance of the vehicle.Permanent magnet synchronous motors have the advantages of high efficiency and high power density,and have been widely used in the field of electric vehicles.Compared with traditional round wire permanent magnet motors,the hairpin winding permanent magnet motor with higher power density is a hot and difficult problem in the research of electric vehicle driving motors.Therefore,this thesis focuses on the complex layout of the hairpin winding and the high eddy current loss under high-speed conditions.Based on this,this thesis studies the end connection method of the hairpin winding,the method to suppress eddy current loss and the motor efficiency.The research of this thesis is as follows:Firstly,based on the characteristics and process requirements of the hairpin winding,this thesis proposes the design method and principles of the hairpin winding,and designs the end-winding connection for two commonly used pole slot combinations of drive motors with 2 and 3 slots per pole per phase,completing the design schemes for different parallel branch numbers,full pitch and short pitch winding groups.According to the design requirements of a high-speed motor,an electromagnetic design scheme for a 6-pole 54 slot hairpin winding motor was completed.The rationality of the electromagnetic design was demonstrated through simulation analysis of the motor’s magnetic field distribution and other electromagnetic properties.Secondly,the influencing factors and optimization methods of eddy current losses are revealed.The preliminary designed motor with hairpin winding is taken as the research object,focusing on the issue of large eddy current losses in the rectangular conductors of the hairpin winding.The methods proposed include optimizing the stator slot topology,increasing the number of generator winding layers,and dividing the conductors to suppress eddy current losses.The distribution of eddy current losses in the rectangular conductors of each layer of the hairpin winding is studied,and the method of dividing the conductors at the slot is pointed out to weaken the eddy current losses.The effectiveness of the optimization scheme is verified through finite element analysis.A method of end-twist conversion is proposed to suppress the circulating losses caused by the divided conductors at the slot of the hairpin winding.The circulating losses of the hairpin winding before and after commutation are analyzed using the leakage inductance potential method.Finally,the loss model of permanent magnet motor with hairpin winding is established,and the full-domain operating efficiency of the motor is calculated to obtain the Map diagram of the full-domain efficiency of the motor.The mathematical and simulation models of the studied pure electric vehicle power system are established through theoretical calculations,and the parameters of the drive motor are input into the simulation model.The efficiency characteristics of the permanent magnet motor with conventional hairpin winding motor and slotted split-strand hairpin winding are also compared under CLTC conditions to analyze the rationality of the split-strand hairpin winding motor in practical engineering applications under vehicle test cycle.