| The problems of energy shortages and environmental pollution have accelerated the development of new energy vehicle technology.Induction motors have become one of the important power sources for new energy vehicles,especially pure electric vehicles,due to their safety and reliability,low control cost,high technical level,and high temperature demagnetization.The stator winding of induction motor is the most vulnerable part of the motor,so controlling the temperature within a certain temperature rise limit is a problem that must be considered in the design of an electric vehicle motor.In this paper,the production principle and calculation method of iron core loss,winding loss,mechanical loss and stray loss were discussed at first.The heat transfer methods such as heat conduction,thermal convection and heat radiation in the motor are analyzed to discuss the characteristics of the heat transfer process of the motor and the problems that should be noticed.According to the theory of electromagnetic field,a three-phase squirrel-cage induction motor field-circuit coupled model was established.Firstly,Maxwell was used to analyze the influence of the stator air gap,stator core outer diameter and stator axial length on the electromagnetic performance of the motor,and the analysis was optimized.The results of the transient electromagnetic analysis were conducted to investigate the variation of the start-up performance of the motor and the magnetic flux distribution and magnetic density distribution of the motor.After calculating the loss data of the optimized motor,the equivalent treatment of the electric wire of the motor,the stator-rotor air gap,and the insulation components was made,which simplifies the solving model of the motor.Building three-dimensional simplified model of motor based on structural features of induction motor.The influence of the number of flow channels in the motor casing on the temperature distribution of the motor was studied under the condition that the total flow rate was fixed.It was found that the larger the number of flow channels,the lower the temperature rise of the motor windings.On this basis,the influence of the liquid flow velocity in the casing flow channel on the temperature distribution in the motor was also studied.The greater the fluid velocity,the better the cooling effect and the lower the stator winding temperature.The temperature gradient of the effective part of the slot top winding become smaller,and the temperature gradient of the slot bottom winding become larger.Under forced convection conditions,the fluid medium was analyzed and the effects of different ratios of glycol water mixture,water and oil on the temperature distribution of the motor were obtained through simulation.With the increase of ethylene glycol ratio in the mixture,the cooling effect of the fluid became worse.but the temperature range of the motor was increased.Finally,the influence of the runner structure on the temperature of the motor was also studied.In this paper,a simplified shell model was proposed,and the influence of fin height,width,number and width of rib plate on the shell temperature was obtained by using the orthogonal analysis method.Through simulation analysis,the correctness of the optimal scheme was verified.In the same environment,the influence of optimized channel structure on the temperature distribution of the motor was also simulated.The optimized flow channel structure model could significantly improve the heat dissipation of the chassis and reduce the temperature of the stator windings. |
