Optimization Design And Fault Research Of High-speed Permanent Magnet Generator Based On Multi-physical

With the development of science and technology,the power system with high-speed permanent magnet generator(HSPMG)as the core has been widely used in aerospace,gas turbine and flywheel energy storage due to its advantages of high efficiency and high-power density.As the core of the system,the HSPMG needs to solve complex problems in electromagnetic performance,heat dissipation,vibration,and mechanical structure.Therefore,it is of significance to have some research on HSPMG.In this paper,a 40 k W,20000r/min HSPMG with toroidal windings is studied to optimize the electromagnetic field design,and the temperature distribution and vibration response are further analyzed using multi-physics field simulation to improve the safety and stability performance of the HSPMG.Aiming at the problem that the magnetic flux leakage generated by the toroidal windings under high frequency conditions will generate shell eddy current loss in the generator,the shell eddy current loss is analyzed.Based on Laplace and Poisson equations,an analytical calculation model of the shell eddy current loss is established.The analytical formula of the shell eddy current loss is derived,the influencing factors of the shell eddy current loss are elucidated.By using the finite element method(FEM),the influence of the shell structure and the shell material on the shell eddy current loss is studied,the mechanism of nonlinear variation of eddy current loss is revealed,and the design scheme with the minimum loss is obtained.The eddy current loss of HSPMG under asymmetric and nonlinear load conditions is studied,and the influence of load on the eddy current loss is obtained.The oil separator in the air gap region increases the reluctance in the main magnetic circuit of the generator,resulting in a decrease in the excitation performance of the permanent magnet.A cooling structure using a weak magnetic oil separator is proposed,which can effectively reduce the reluctance in the air gap region and increase the excitation effect of the permanent magnet.Using the analytical method,the no-load induced electromotive forces of the HSPMG with different permeability oil separators are calculated.The adjusting magnetic field character curve of oil separator permeability is obtained.The influence of the electromagnetic parameters of the magnetic oil separator on the generator output performance is studied by FEM,and the mechanism of the nonlinear variation of the generator output performance with the permeability of the oil separator is obtained.In addition,the distribution of the air-gap magnetic field and electromagnetic force of generators with different permeability oil separators is further analyzed,and the reduction mechanism of the magnetic oil separator on the harmonic is revealed.The influence of inter-turn short fault(ITSF)on the performance of HSPMG with the toroidal winding(TW)is studied,the parametric equation of TW fault is analyzed,and the variation of winding electrical parameters after fault is obtained.The electromagnetic characteristics of the HSPMG after the ITSF are analyzed by the field-circuit coupling method.The space-time distribution of the air-gap magnetic field under fault is obtained,and the mechanism of asymmetry in magnetic field is revealed.Based on the Fourier transform method,the characteristics of the electromagnetic force under different working conditions are analyzed,and the characteristics of the electromagnetic force harmonic caused by the short-circuit current are obtained.Using the 3D-modal model of the generator stator,the vibration mode and natural frequency of the stator are analyzed.According to the above research results of the electromagnetic force characteristics,the electromagnetic force excitation source is applied to the stator model,and the vibration response of the HSPMG under different working conditions is calculated by combining the transient dynamics and harmonic response analysis.The influence of oil separator with different permeability on generator vibration is studied,it is confirmed that the magnetic oil separator can reduce the vibration amplitude of generator.The vibration characteristics of generator under fault condition are studied,and the vibration signal characteristics of the generator after the ITSF are obtained,which can provide reference for generator fault diagnosis.Based on the calculation of the generator electromagnetic losses,the 3-D temperature field calculation model of the generator is established.The temperature rise of the generator under different shell materials is studied,the influence of different shell materials on the internal heat transfer of the generator is revealed.The influence of oil separators with different thermal conductivity on the internal heat exchange of the generator is analyzed,the internal temperature distribution characteristics of the generator are obtained.The temperature distribution of the winding and permanent magnet is given,which is important to prevent insulation failure and thermal demagnetization of the generator.The electromagnetic test and temperature rise experiment of the generator is carried out,while the experimental and finite element results are compared to verify the correctness of the model.