Design And Research Of In-wheel Motors For A00-class Electric Vehicles

The "small figure" A00 car is the most suitable tool for urban travel for the city traffic jams and parking spaces in short supply.Although major automobile enterprises have successively launched A00 level electric vehicles,China is still in the initial stage of research on hub motors suitable for A00 level electric vehicles,lagging behind western countries.In response to the national call to keep up with the development of automobile era,this paper had carried out performance calculation,structure design,the simulation analysis and experimental research for the wheel hub motor of A00 level.The studied hub motor was permanent magnet synchronous motor in the form of external rotor direct drive.The structure and dynamic performance parameters of A00 car are analyzed and we determined the design target and the overall design plan of the hub motor.And,we analyzed the hub motor's electromagnetic field.The research showed that slot width and air gap thickness mainly affected cogging torque and output torque of hub motor.The slot width mainly affected the cogging torque and torque ripple of the hub motor,and had little effect on the amplitude and waveform of the back EMF.When the slot width is 2.7mm,the cogging torque was the smallest,which was more than 3mm.While the increase of the cogging torque was obvious,and the change of the output average torque was little,but the torque ripple was obviously increased.The thickness of permanent magnet had great influence on the output torque of motor,but it had almost no effect on the back EMF and cogging torque of motor.The electromagnetic field analysis showed that the distribution of the no-load magnetic field was reasonable,the back EMF was 75 V,the sine wave was a sine wave,the average torque was 117N m,the torque ripple was 5%,the eddy current loss and the iron core loss were in a reasonable range.In terms of mechanical structure,the stiffness and stiffness of the motor spindle were analyzed,and the overall modal analysis of the hub motor was carried out.The analysis showed that the safety factor of the motor spindle can still reach 1.9 under the limit condition,and the lowest natural frequency of the hub motor was 275.28Hz,which was far higher than the maximum frequency 17Hz of the wheel hub motor and the highest frequency 28Hz of the road excitation,which indicated that the hub motor would not produce resonance.The rated power of the prototype was 7.5kW,the rated speed was 600rmp and the efficiency was up to 88.4%.The test curve of the prototype showed that the power characteristic and the mechanical characteristic of the prototype were good,which conformed to the performance requirements of the A00 grade electric vehicle for the driving motor.This paper only made some research on the design of the wheel motor used in the domestic A00 electric vehicle for the limited ability,which can provide reference for the design method of similar wheel motor.