| In recent years,with the rapid development of medium and high voltage electronic converter technique,and rare earth permanent magnetic materials of super-high performance,NdFeB rare earth permanent magnet synchronous motors(PMSMs)has ushered in another opportunity for rapid development in new field.Compared with conventional electric excitation and induction motors,PMSMs have notable advantages,such as simple structure,reliable operation,small volume,light quality,good dynamic performance and so on.But the troubles of vibration and noise produced by operating PMSMs have been a difficult problem puzzling people.The problems of serious vibration and noise have become a key factor which can decide whether the products can be stable operation can meet the standard limits or not.Therefore,developing researches on vibration and noise of the PMSMs,solving the key technologies in product design,improving the operating performance of the PMSMs and expanding the application fields of the PMSMs can have important influence on the development of national economy.In this paper,combining with the research status of the domestic and foreign about the vibration and noise of motor,the characteristics of the vibration and noise of surface-mounted permanent magnet synchronous motor(SMPMSM)with fraction-slot windings are analyzed and the main contents are as follows:(1)Magnetic field of the SMPMSM is analyzed.The radial magnetic flux density at air gap is respectively calculated by analytical and numerical methods,which is in good agreement with each other.The influence of open slot of stator on the radial magnetic flux density at air gap is obtained by theoretical deduction.The order and the frequency of the radial electromagnetic force wave at air gap are investigated,and the varied laws of the order and the frequency of the radial electromagnetic force wave at air gap produced by different magnetic fields are obtained.The harmonic force sources of magnetic field which can produce radial electromagnetic force wave with low order and large amplitude are found out.(2)Natural frequencies of the SMPMSM are studied.The numerical method is applied to calculate the circumferential natural frequencies of cylindrical shells with different length,wall thickness,mean diameter,diameter-thickness ratio,size and installation position of terminal box.The influences on the circumferential natural frequencies of cylindrical shells are investigated.An analytical method considering diameter-thickness ratio for calculating circumferential natural frequencies of cylindrical shells is developed.Compared with the numerical results,the validity of the analytical method is verified.The analytical formulas considering stiffness error of model simplification are proposed to calculate the circumferential natural frequencies of stator core and motor case.The circumferential natural frequencies of stator structure are respectively calculated by analytical,numerical and experimental method.Furthermore,the analytical method considers diameter-thickness ratio,stiffness error of model simplification and existence of terminal box,mutual constraint of each component and other errors.Compared with the numerical and the experimental results,the relative errors are respective within|2.52%|and|7.42%|.(3)Flow field of the SMPMSM is investigated.The coupling calculation on flow field and noise field of internal air basin(considering the space between the two permanent magnets in air gap)and fan-duct basin of the SMPMSM is respectively carried out.And thereby the regions which can produce the higher noise are identified,namely the space between the two permanent magnets in air gap and the contacting regions between the impeller outlet of cooling fan and the ducts.The configuration on permanent magnets of 5 big(48°)/ 3 small(40°)poles and 3 small poles connected together is adopted to reduce the noise of internal air basin of the SMPMSM,and reduced by 1.1dB;the 15 mm relative space between the ducts is used to decrease the noise of fan-duct basin of the SMPMSM,and decreased by 1.4dB.The relationship among the rotational speed of cooling fan,the aerodynamic noise and mass flow of fan-duct basin is determined.(4)The influence of iron loss harmonics on the noise of the SMPMSM is researched.The numerical method is adopted to analyze the influence of different working conditions,voltage modulation indexes in inverter controlled by pulse-width modulation(PWM),rotational speeds of motor,inverters and control methods on the iron loss harmonics of the SMPMSM.The results show that: the iron losses of the SMPMSM produced at load operation are larger than no-load operation’s and the iron losses of the SMPMSM generated at no-load operation are larger than no-current operation’s.If the voltage modulation indexes in inverter controlled by PWM is reduced or the rotational speed of the SMPMSM is increased,the iron losses of the SMPMSM will be increased.Compared with the silicon insulated gate bipolar transistor(Si-IGBT)inverter excitation,the silicon carbide metal-oxide-semiconductor field-effect transistor(SiC-MOSFET)inverter excitation can effectively reduce the iron losses of the SMPMSM.Compared with the PWM control,the pulse-amplitude modulation(PAM)control can also effectively reduce the iron losses of the SMPMSM.At the working conditions of the lower iron losses,because of the less harmonic content of voltage and current,the noise values of the SMPMSM will also be reduced.(5)Noise of the SMPMSM is tested and discussed.The spectra of sound pressure level(SPL)and the noise values of the SMPMSM are obtained by experiment at different rotational speeds,switching frequencies and loads.The frequencies and main peaks of SPL spectrum are obtained.The reasons for generating noise of the SMPMSMs are researched from three aspects,namely,mechanical noise source,aerodynamic noise source and electromagnetic noise source.Different measures for decreasing noise of the SMPMSMs are presented,namely,increasing coaxiality,opening auxiliary slots in the middle of stator teeth,enhancing switching frequency,increasing the wall thickness of stator structure,reducing the current harmonics and so on.A comprehensive method(increasing coaxiality,opening auxiliary slots in the middle of stator teeth and increasing the wall thickness of stator structure)is proposed to decrease noise of the SMPMSMs.The method can make noise value of the SMPMSMs reduced by 4.7dB(A)at 2000r/min rated speed,4kHz switching frequency and full load.In addition,the sharpness and loudness of the SMPMSMs are also respectively decreased by 0.522 acum and 6.97 sone at no load. |
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