| The fractional slot concentrated winding permanent magnet(FSCW-PM)machines have the advantages of high power density,high efficiency,low torque ripple and high reliability,it has broad applications in engineering fields such as electric vehicles,ship propulsion and all-electric aircraft.However,the FSCW-PM machines contain rich armature magnetomotive force harmonics.The characteristics of the near pole-slot combination will produce low-order radial electromagnetic force with a large amplitude,which is easy to excite severe electromagnetic vibration and noise.Based on Maxwell's stress equation,this paper deduces the semi-analytical formula of radial electromagnetic force of FSCW-PM machines,and establishes the internal relationship between PM and armature flux density harmonic and radial electromagnetic force.Taking a 12-slot/10-pole FSCW-PM machine as the research object,the low-order radial electromagnetic force suppression method is designed and analyzed from three aspects: stator structure,winding connection and rotor structure without reducing the torque.The vibration and noise prediction model of PM machine is constructed.The mode,vibration and noise of 12-slot/10-pole FSCW-PM machines are calculated by electromagnetic and structural finite element numerical calculation method.The effectiveness of the new structure to reduce the electromagnetic vibration of the machine is verified,The PM machine experiments of mode and vibration further verify the correctness of the radial electromagnetic force,vibration and noise analysis.The main contents of study are as follows:1.According to Maxwell's stress equation,the expression of radial electromagnetic force is deduced.The finite element method is used to calculate the flux density and radial electromagnetic force of the machine.The two-dimensional Fourier analysis of the radial electromagnetic force is carried out to explore temporal and spatial distribution law;the intrinsic relationship between the slot and pole combination and spatial order of the radial electromagnetic force is revealed.2.The intrinsic relationship between radial electromagnetic force and flux density harmonics is analyzed.The methods to reduce the lowest order radial electromagnetic force are designed and analyzed from three aspects: stator structure,winding connection and rotor structure without reducing the power density of the 12-slot/10-pole permanent magnet motor,and their validity are verified by using finite element calculations.3.The influence of various structural components of the machine on the mode of the whole machine is calculated by finite element software.A multi-physics prediction model for motor vibration and noise is established.The vibration and noise characteristic of the 12-slot/10-pole FSCW-PM machine under load operation is calculated,and the suppression effect of the new structure of the motor on the electromagnetic vibration of the motor is verified.4.The mode and vibration experimental platform of the 12-slot/10-pole FSCW-PM machine is built to measure the modal frequency of the machine in a free state,and the vibration acceleration value of the machine under no-load and on-load operation is also measured.By comparing the electromagnetic vibration prediction and test values of the 12-slot 10-pole FSCW-PM machine,the accuracy of the prediction model and the effectiveness of the low-noise machine design methods are verified. |
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