Loss And Temperature Analysis Of Permanent Magnet Synchronous Motor For Electric Vehicles

As the problems of energy crisis, environmental pollution and the greenhouse effect go worse, the auto industry puts forward higher requirements of energy saving and emission reduction. So developing new energy vehicles has become the inevitable trend in the automobile industry changes. The "twelfth five-year" special plan of electric vehicle technology developing mentioned that the state would intensify efforts to national science and technology plan and continue to support electric vehicle technology innovation. For new energy electric vehicles, its core is to drive motor driver system, and merit or defect of driving motor performance directly determines the property of new energy electric vehicles.In this paper the basic performance parameters of the motor was determined firstly, and then the electromagnetic field model of permanent magnet synchronous motor was established, designed and optimized in allusion to the problem of power loss and temperature rise of electric car’s permanent magnet synchronous motor; Secondly the wastage of the permanent magnet synchronous motor was analyzed in this paper; Thirdly,two-direction coupling model of electromagnetic field and temperature field was established for accurate analysis of the whole motor temperature rise; Finally, motor loss and temperature rise was verified by experiment.Specific work was completed as the following:First of all, actual operation condition of pure electric vehicle was analyzed, then drive motor parameters are matched. Besides, the overall design of the motor and its electromagnetic optimization were completed.According to the performance requirements of electric vehicle driving motor and with the help of finite element analysis method, the basic size ofpermanent magnet synchronous motor, the coordination between pole and slot and rotor structure’s electromagnetic parameters were designed. In addition, the cogging torque of the motor was optimized by different ways.Secondly, all kinds of loss of the motor were analyzed, then the iron loss calculation model was established. The magnetic field distribution of prototype was analyzed by using the finite element analysis software, then the permanent magnet motor flux density wave form was analyzed gradually and accurately by the way of method of equal effects of sinusoidal wave method, the radial and tangential method and Fourier decomposition method. And then ferromagnetic materials and harmonic current, the factors which affect the iron loss, were calculated.Thirdly, calculation model of permanent magnet synchronous motor in 3D transient temperature field is established, then the boundary conditions, the thermal conductivity and coefficient of heat transfer etc.were found out. Then prototype’s coupling calculation of temperature field and electromagnetic field under control of constant torque strategy was realized by the way of iterative method, and compared with one-way coupling.Finally, the performance of the designed prototype was verified and tested. Then separate the loss of prototype test results and compare it with theoretical calculation value of iron loss to verify the correctness of calculation method, and analyzed the relations between all kinds of loss and the temperature rise. It’s to provide reference for reducing the temperature rise of permanent magnet synchronous motor in electric vehicles and the optimization design.