| There are several requirements for the asynchronous motor of electric SUV,namely,large and low torque ripple,low loss,high efficiency and low vibration and noise,which is the prominent problem at present.And further improvement also needs to be done in torque output,loss as well as efficiency.Since asynchronous motor is a nonlinear system with multiple variables and close coupling,all the above performances interact with each other to some extent,and how to balance those indexes is the key to improve asynchronous motor’s comprehensive performance.As an important means to improve this comprehensive performance of asynchronous motor,it is of great significance to explore the influencing factors and their internal relations to improve the performance of electric SUV.A series of studies have been done: the study of vibration and noise of asynchronous motor based on the vibration test of asynchronous motor and the noise test of integrated electric drive system;the electromagnetic model of asynchronous motor established and verified on the basis of reasonable hypothesis,and its comprehensive performance analyzed combining with the driving performance test of asynchronous motor;and the comprehensive performance of asynchronous motor evaluated based on electromagnetic simulation model and various studies of asynchronous motor.The results show that the difference between simulation and test efficiency is small,the rated torque is basically the same,and the corresponding error of harmonic frequency of electromagnetic force and vibration frequency is 2.76%,which verifies the correctness of the electromagnetic model.Also,according to those tests,the change trend of electromagnetic performance is similar under different loads,and the motor whistling noise on near 1620 rpm is obviously noisy,whose comprehensive performance needs to be improved.Based on the electromagnetic model,how air gap flux density and electromagnetic force density will affect the comprehensive performance of asynchronous motor is discussed.Also,the influence mechanism of vibration and noise of asynchronous motor is studied through modal simulation analysis,and the correctness of the model is verified.The results show that the amplitude and harmonic content of air-gap flux density has a great influence on torque output characteristics,loss and electromagnetic force,the main cause of vibration and noise is radial electromagnetic force of 4th,8th,56 th,60th,64 th,68th and 72 nd order,the second-order radial mode of stator core is the main reason for motor whistling near 1620 rpm,and the natural frequency error between simulation and test is less than 5%,which verifies the correctness of modal analysis model.On the basis of the electromagnetic model,the influence of air gap length,width and tooth thickness of stator slot,rotor slot angle and rotor slot number on the comprehensive performance of asynchronous motor are studied as follows: increasing air gap and reducing stator slot width can improve efficiency,minimize loss,torque ripple and electromagnetic vibration,but reduce torque;proper width and tooth thickness of stator slot can balance the output torque and torque fluctuation,and rotor slot can further reduce the torque ripple as well as eliminate the tooth harmonic caused by it;Different rotor slot numbers will lead to electromagnetic force tooth harmonic.With the far slot matching,the output torque decreases with the increase of rotor slot number,which has little effect on loss and efficiency,so changing the rotor slot number is not conducive to improving the comprehensive performance of the asynchronous motor.The optimal solutions are proposed as follows: compared with the original motor,the maximum efficiency of the motor with 0.65 mm air gap,0.8 ° slot width,0.75 mm tooth thickness and rotor skew 1 slot increases by 1%,which has little influence on the rated torque.Although the peak torque decreases,it still meets the requirements of electric SUV with large load.And the torque fluctuation and loss are greatly reduced.Since the harmonic order of radial electromagnetic force density in main working conditions is reduced significantly,the vibration and noise of asynchronous motor can be solved effectively. |
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