Research On High-efficiency Interval Of High Power Density Permanent Magnet Synchronous Motor For Pure Electric Passenger Bus

With the development of technology,cars have become one of the most important ways of transportation in people's life.Traditional fuel vehicles not only consume limited petroleum resources,but also pollute the environment.It is urgent to find new energy electric vehicles to replace the traditional fuel vehicles.The 80 kW pure electric passenger bus driving motor of this thesis selects permanent magnet synchronous motor(PMSM)with excellent overall performance.Driving motor is not only the power core of the whole vehicle,but also the main energy consumer,whose quality directly affects the performance of the vehicle.Due to the limitation of installation size and overall weight,the driving motor requires high power density.At the same time,in order to increase the single charging mileage of pure electric passenger bus,the working point of the driving motor should be located in high-efficiency interval as far as possible.So this thesis mainly researches on power density and high-efficiency interval of the permanent magnet synchronous motor for driving motor.Firstly,the research background,purpose and significance of this thesis are introduced,the performance requirements of pure electric passenger bus driving motor are summarized,and the performance characteristics of different types of motors are compared.Then,the research status of power density and high-efficiency interval of permanent magnet synchronous motors for pure electric passenger bus at home and abroad is summarized.Given the main technical parameters and the housing structure of the pure electric passenger bus driving motor,the electromagnetic structure is designed.Firstly,the rotor structures of permanent magnet synchronous motor are compared and selected,which can not only meet output torque but also flux weakening.By comparing the cogging torque and losses of the different pole and slot matching motors,the 8-pole and 48-slot matching is more suitable for the 80 kW pure electric passenger bus driving motor.The double layer short distributed winding and pear shaped slot of stator are selected.At the same time,No-load back electromotive force(EMF)affecting losses and efficiency of the driving motor is reasonably valued.The electromagnetic load and the stator split ratio which affect the power density of the driving motor are studied,and the aspect ratio,main size and optimal stator split ratio are obtained.Then,the rationality of motor design is verified by temperature field simulation andthe power density of driving motor is obtained.Aiming at the study of the high-efficiency interval of permanent magnet synchronous motors used for pure electric passenger bus,four internal permanent magnet synchronous motors(IPMSM)with different rotor structures are designed in the thesis.Firstly,the distribution of the main loss maps and total loss maps of these driving motors are compared and analyzed.Then,the efficiency maps and their high-efficiency interval distribution are analyzed and studied.The main factors affecting the range and position movement of the high-efficiency interval are found and the moving directions of different pure electric passenger bus driving motors' high-efficiency interval are introduced.