Research And Design Of High Performance Low Voltage Electric Drive System

With the rapid development of EV,electric drive system has become a research hotspot in the automobile industry.Compared with the high voltage electric drive system,the low voltage electric drive system has the advantages of high security,high reliability,low cost,good electromagnetic compatibility,and so on.It has great application prospects in the future.The low voltage electric drive system is studied,and a high performance low voltage electric drive system is designed.The magnetic circuit structure,operation performance,air cooling and water cooling structure of the double winding switching type drive motor are designed and analyzed,and the prototype is made and the low voltage electric drive system experiment platform is built for related experiments.The main contents are as follows:(1)According to the dynamic performance requirements of high performance and low voltage electric drive system,the double winding switching design of drive motor is proposed and theoretical analysis is carried out.Based on the given basic parameters of the driving motor,the magnetic circuit structure of the motor is designed.In order to realize the convenience of double winding switching,the manual/automatic winding switching control system is designed and the selection basis of rated speed point of double winding switching is given.In order to reduce the temperature rise of the motor,an axial water cooling structure of the casing is designed.In order to compare the heat dissipation effect of the axial water cooling of the casing and the circumferential water cooling of the casing,a copper tube structure embedded in the outer wall of the casing is designed to simulate circumferential water cooling of the casing.(2)The uneven air gap was used to optimize the performance of double winding switching drive motor,and the influence of different convex distance of rotor on the motor performance was analyzed.The results show that the uneven air gap can reduce cogging torque,torque ripple,back emf harmonic content and so on.Secondly,the influence of the double winding switching design on the motor performance was studied,the operation performance of the motor in series and parallel winding mode is compared and analyzed.The results show that the double winding design can broaden the range of motor speed and torque,so that the motor has the operating characteristics of low speed and high torque and high speed and low torque.Then,the effect of double winding switching on motor loss and efficiency was studied,and the motor loss in series and parallel mode of winding at rated power and rated speed was compared and analyzed.The results show that the motor loss in parallel mode is lower.Finally,the efficiency MAP of the motor in series and parallel mode is analyzed.The results show that the double winding switching design can broaden the high efficiency range of the motor and improve the driving range of the electric drive system.(3)Based on the water cooling structure design and loss analysis results of double winding switching drive motor,the temperature distribution of natural air cooling and water cooling was studied.Based on the principle of thermal analysis,the thermal analysis model and solving conditions of the motor were determined,and the temperature distribution of the parts of the motor under natural air cooling was analyzed.Based on the basic theory of fluidstructure coupling,the inlet velocity and flow state of the coolant in the axial water cooling structure and the simulated circumferential water cooling structure of the casing were determined.The cooling effects of the two kinds of water cooling structures were compared and analyzed.The results showed that: The heat dissipation effect of the axial water cooling structure of the casing is obviously better than that of the simulated circumferential water cooling structure of the casing.The adoption of the axial water cooling structure of the casing can ensure that the temperature of all parts of the motor is lower than the allowable temperature,so as to ensure the safe,efficient and stable operation of the motor..(4)The double winding switching motor was made and debug,and the high performance and low voltage electric drive system was set up.The simulation results were verified experimentally,and the results showed the reliability of the simulation results.