Research On Vibration And Noise Of Permanent Magnet Motor Under Harmonic Current

Since the20th century, with the rapid development of power electronic technology, rareearth permanent magnet materials and materials processing, permanent magnet synchronousmotor(PMSM)has been rapid promoted and applied. Most of the PMSM are supplied byinverter. If the motor supplied by inverter, it will generate harmonic currents in the motorwindings, so this thesis mainly studies the influence of harmonic current on the vibration andnoise of PMSM supplied by inverter. Including several parts as following:Firstly, the harmonic current of inverter power supply were analyzed, the result showsthat the high frequency of harmonic current mainly distributes near the switch frequency andits frequency doubling when the PMSM under inverter supply. As the motor is three phaseand the stator of the motor is connected in star, the low frequency of harmonic currentmainly refers to the5th and7th harmonic current. This thesis mainly studies the effect of lowharmonic current to the vibration and noise of PMSM.Secondly,2D transient magnetic field and3D transient magnetic field are simulated andevaluated based on Finite Element Method(FEM)under different harmonic current to obtainthe electromagnetic force as load to simulate and calculate the vibration noise of the motor.The effects of different amplitude of5th and7th harmonic currents superposited withfundamental on vibration and noise of the motor is studied to find the rule. Analysis showsthat, the low order harmonic current could not change the frequency of electromagnetic force,and low harmonic current plays a role in vibration absorption and noise reduction. What ismore, the modal analysis of the motor is also been simulated and analysised, including thestator system, rotor system and the total motor system, and obtains the variation rule ofnatural frequency of each parts of the motor and gets the rotor critical speed. The simulationresults show that the natural frequency of each parts of the motor is better to avoidelectromagnetic force frequency, and the resonance phenomenon will not occur.Finally, the vibration experimental has been done on the motor to verify the accuracy ofvibration and noise simulation and vibration modal calculation, and the impact of differentcarrier frequency of inverter to the vibration acceleration of the motor is studied. Theexperimental results show that the accuracy of vibration of three-dimensional calculationresults is superior to two-dimensional calculation, and the error of three-dimensionalcalculation result can achieve less than5%, and the modal calculation of whole machine is about5%, and with the increasing of inverter carrier frequency, the vibration acceleration ofthe motor is increasing.