| In recent years,permanent magnet synchronous motors(PMSMs)have been widely used in electric vehicles,elevators,medical devices,rail transit and other fields due to its high power density,high efficiency and simple structure.In particular,compared with surface-mounted permanent magnet synchronous motors,the internal permanent magnet synchronous have attracted more attention for its higher torque utilization rate and wider speed range.However,the use of high-strength permanent magnets aggravates the torque pulsation,and makes the harmonic distribution of the air-gap magnetic density more complex.The resulting vibration and noise problems will cause hearing loss and even damage the nervous,cardiovascular and other human systems.As one of the common faults in rotating electrical machines,the rotor eccentricity will cause uneven distribution of air gap magnetic conductivity,which will distort the air gap magnetic field,and will also intensify the electromagnetic vibration and noise.Based on the built-in permanent magnet synchronous motors considering different pole-slot match effect,this paper compares the electromagnetic forces and vibration and noise between the healthy motors and the motors with dynamic and static eccentricity,what’s more,different stator winding arrangements are considered in the motor with rotor dynamic eccentricity.The main works are as follows:(1)The harmonics of radial electromagnetic force are the main sources of electromagnetic vibration of permanent magnet synchronous motors.First of all,the expressions of air gap permeability of a healthy and a rotor eccentric permanent magnet synchronous motors with different pole-slot combination are analyzed,and then the air gap magnetic density is obtained according to the magnetomotive force-magnetic conductance method under a)only considering the effect of permanent magnet,b)considering the stator fundamental current,and c)considering the effect of harmonic currents of inverter power supply.Finally,the temporal and spatial characteristics of electromagnetic force are calculated by Maxwell stress tensor method,and the universal expression of electromagnetic force harmonic components are derived.(2)The finite element analysis of the healthy motor and the rotor eccentric motor is carried out respectively.The finite element models of the an 8-pole 48-slot and an 8-pole 36-slot built-in permanent magnet synchronous motors with a power of 10 kW are established.First,the finite element calculation is carried out in the two-dimensional static and transient field for the two motors under no-load and sine wave current supply conditions.Then,considering the stator harmonic currents,a combined simulation model is built based on the vector control method for calculation.The air-gap magnetic density and electromagnetic force generated by low-frequency current harmonics and high-frequency current harmonics under the joint simulation are compared,and the theoretical analysis results are verified.(3)For the rotor dynamic eccentricity fault,the simulation results of air gap magnetic density and electromagnetic force are obtained by joint simulation considering the winding balance current with different number of parallel branches,then the unbalanced magnetic force with different winding arrangements are compared.The results show that the balance current caused by rotor eccentricity will mitigate the air gap distortion,thus weakening the electromagnetic force amplitude,suppressing electromagnetic vibration and unbalanced magnetic force.It should be noticed that the balance current only exists in the motor with parallel branches.(4)The modal shapes and frequencies of the healthy motor and the rotor eccentric motor are analyzed,simulated and tested.First,the modal simulation results of the stator and the stator-frame system are compared,which shows that the natural frequency of the motor will be increased with the consideration of the casing.Then,the prototypes of a healthy motor and a motor with dynamic eccentricity with the basic electrical and geometric parameters consistent with the simulation models are made respectively.Finally,the complete machine modes of the two motors are tested respectively,and the more practical modal shapes and natural frequencies are obtained.(5)An experimental platform for the electric drive and vibration and noise acquisition of the two motors is built,the electromagnetic performance and vibration and noise are tested and compared.The results show that the dynamic eccentricity will increase the amplitude of the overall vibration acceleration where the vibration amplitude of the fundamental frequency is more prominent.The vibration characteristics of different winding arrangements are also different,the electromagnetic vibration and noise with the balance current in the parallel branches will be weakened to different points according to the number of it.The theoretical analysis and simulation results of electromagnetic force and electromagnetic vibration are well verified by experiments. |
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