| The interior permanent magnet synchronous motor(IPMSM),which has high power density and wide range of constant torque operation,is widely used as the driving motor of electric vehicles.The windings of the IPMSM will inevitably contain abundant harmonic currents when it is in normal operation under the control of the inverter.Further,the harmonic electromagnetic forces caused by harmonic currents will worsen the vibration and noise performance of the IPMSM.Therefore,it is of great practical significance to study the variation pattern of air gap magnetic field and electromagnetic force of IPMSM under harmonic currents.(1)Analytical modeling and characteristic analysis of air gap magnetic field and electromagnetic force of IPMSM.Firstly,the analytical model of no-load air gap magnetic field of IPMSM considering complex rotor structure and complex magnetic circuit structure was established by semi-analytical modeling method.Secondly,the analytical model of armature reaction magnetic field considering stator-slots and permanent-magnet-slots of rotor effect was established by using vector superposition method and permeability function method.Then,according to the magnetic field superposition method and Maxwell stress tensor method,the analytical models of air gap magnetic field and electromagnetic force of IPMSM were established respectively,and the spatial orders and frequency characteristics of air gap magnetic field and electromagnetic force were revealed.Finally,the accuracy of the analytical model of air gap magnetic field and electromagnetic force was verified by the finite element simulation results.The results prove that,the special structure of the permanent-magnet-slots of the IPMSM will lead to the occurrence of order 2kp in the spatial order of the air gap magnetic field,and the occurrence of component 2kfc in the frequency characteristic,where p is the logarithm of the electromagnetic poles of the motor,and fc is the fundamental frequency of the currents at that rotational speed,k is a positive integer.(2)Analytical modeling and characteristic analysis of air gap magnetic field and electromagnetic force under harmonic current.Firstly,three-phase harmonic current data of IPMSM under different working conditions were collected by experiment method on the motor test bench.Based on the test data,analytical models of harmonic currents,which can describe different harmonics,were established.Then,different harmonic currents were introduced into the analytical model of the air gap magnetic field and electromagnetic force of IPMSM respectively,and the analytical models were obtained,which can calculate the air gap magnetic field and electromagnetic force of IPMSM under different harmonic current.The influence of harmonic currents on the air gap magnetic field and electromagnetic force of IPMSM was revealed.The results prove that the harmonic currents interact with the component 2kfc of the frequency generated by the permanent-magnet-slots,which further enriches the frequency components of the air gap magnetic field and electromagnetic force of IPMSM.(3)Experimental study on IPMSM.An 8-poles-48-slots IPMSM for electric vehicle was used as the research object,the analytical calculation model of no-load air gap magnetic field and electromagnetic force of the IPMSM proposed in this thesis were tested and validated respectively.Firstly,the no-load air gap magnetic field of IPMSM was measured directly on an ultra-thin no-load air gap magnetic field test bench at the order of 10-1 mm magnitude.The accuracy of the analytical calculation model and the finite element model of the no-load air gap magnetic field are verified by the test results respectively.Secondly,no-load back-EMF acquisition experiments were carried out on the motor test bench to indirectly verify the accuracy of the analytical model of no-load air gap magnetic field and the finite element simulation model.Finally,the electromagnetic torque measurement test was carried out on the motor test bench,and the accuracy of the electromagnetic torque analytical model and finite element model was verified by the test results.The results prove that the spatial order of the no-load radial air gap magnetic field of the IPMSM is np±?Qs and the frequency is nfc,where ? is a positive integer,Qs is the number of stator slots.The main frequency of electromagnetic torque is 0.The analytical results and finite element results are in good agreement with the experimental results.The experimental results verify the accuracy of the analytical models and the finite element models of no-load air gap magnetic field and electromagnetic force of IPMSM. |
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