The Study Of Thermal Characteristics In Various Conditions And Cooling System Of Permanent Magnet Synchronous Motor In Pure Electric Vehicle

In recent years, with the urgent requirements of energy saving and emission reduction, together with the national policy guidance and supports, research institutions and automotive enterprises have been carrying out a large amount of research and development on pure electric vehicle and the key components. Drive motor, as one of the three main components of pure electric vehicle system, is very important to be researched and developed. Because of the complex operating conditions of pure electric vehicle, the temperature rising issue of drive motor under the operating conditions is particularly outstanding. If the temperature rising issue of drive motor cannot be efficiently solved, it will affect the performance and lifetime of drive motor, further affects performance and security of the whole vehicle. So it has very important practical significance to research the thermal characteristics and cooling systems of the high power density motor working under complex conditions, such as high torque and high power etc.Based on the analysis of vehicle conditions and requirements for the motor, taking ’the source of heat—the analysis of heat—the treatment of heat’of pure electric vehicle water cooling permanent magnet synchronous motor under the vehicle operating conditions as the main research clue, these aspects, such as the motor loss, the steady state temperature field, the variable working conditions temperature field and the optimization of motor cooling system, were separately systematically researched.Firstly, this dissertation analyzed the different new energy vehicles and motor characteristics with different, power systems. And based on the analysis of vehicle driving cycle, the simulations and tests of motor under two kinds of impact conditions were carried out. Finally the research results were consolidated by the real vehicle testing under the NEDC (New European Driving Cycle) operating mode. Based on the whole vehicle, according to the vehicle performance requirements, the type selection and parameters matching of the vehicle motor were analyzed in detail, and the specific parameters of the vehicle motor were achieved.Secondly, based on the selected vehicle motor, this dissertation mainly studied the stator core loss which is one of the main motor losses. Through the core flux density analysis under different conditions, a much better calculation model of core loss was established. The model not only considered the core loss causing by the rotated magnetization, the local hysteresis loop and the harmonic eddy current, but also introduced the correction coefficient obtained from the experimental data to compensate the effects on the core loss from other factors. Based on the model, the stator iron core loss was calculated under the rated condition and peak condition. Finally, the high accuracy of the model is verified indirectly by the experimental test of the motor.Thirdly, this dissertation established a 3D temperature field calculation model for the PMSM with axial spiral type and put forward an equivalent method for calculating the clearance between the stator and shell, which improved the method of calculation and analysis for the corresponding boundary conditions of the domain; accordingly, the steady temperature field under the rated condition and the dynamic temperature field under the impact condition were simulated. Then a temperature-rising experimental platform about the motor was constructed. Based on the simulation analysis and the experimental results, the accuracy of the equivalent method for calculating the assembly clearance was validated. Furthermore, the contrastive results showed that the temperature rising of the motor with such structure was higher, and it needed to be optimized.Finally, in order to make a better heat dissipation and improve the performance of the cooling system of the motor, the axial helical channel of the motor should be optimized. This dissertation designed three new channel structures such as the axial Z glyph, radial Z glyph and axial i-section glyph. And through the simulation results of the temperature field, the velocity field and the pressure field of these three new channel structures and the axial helical channel structure, it was found that the axial Z glyph channel structure was better. And then, the dissertation determined the optimal water cooling system from the optimization of the channel number, cooling water flow rate and shell materials of the axial Z type water channel. According to the optimized water cooling system, the temperature field of the corresponding motor under the rated condition and impact condition were simulated. At the same time, the results of the simulation were verified by temperature-rise experiments. Through the comparison and analysis of the simulation values and experiment values before and after the motor optimization, we can find that the optimized water cooling system greatly reduced the temperature of the motor. The temperature rising experiments on the optimized motor under the NEDC condition showed that the temperature rising of the water cooling system could meet the complex operating conditions.Through the study of thermal characteristics and cooling system of PMSM in pure electric vehicle, the outcomes can provide certain guidance for thermal design and cooling system design of this type of vehicle motor.