Electromagnetic Analysis And Optimal Design Of The Permanent Magnet Synchronous Machine Based On The Exact Subdomain Method

As the key part of the high performance motion control systems,the permanent magnet synchronous machines(PMSMs)have been widely used in the industrial robots,machine tools,electric vehicles,aeronautics and astronautics products,and so on.However,due to some inherent disadvantages of the PMSMs,such as the slot effect,end effect,and irreversible demagnetization,some problems have still not been effectively resolved in the actual engineering.Meanwhile,the analysis,design and optimization methods of the PMSMs should also be improved.In this thesis,the analytical modeling,electromagnetic analysis and optimal design of the PMSMs are researched based on the exact subdomain(SD)method.The main research work can be summarized as the following six aspects.Part I.Through the motion analysis of the PMSMs,a combined SD model based on an inner SD model and an outer SD model is presented.The field solutions of the inner and outer SD models are obtained by solving the Maxwell's equations and adopting the harmonic analysis method.A unified analysis model is created which can be applied to almost all the surface-mounted rotatory,arc-linear and linear PMSMs,and the selection of the model parameters for analyzing different PMSMs is illustrated.The comparison between the SD model and the finite element model(FEM)is conducted.Part II.An ironless PM machine is analyzed and designed by the SD method through comparing the influence of different rotor types,slot/pole combinations and magnetizations on the electromagnetic characteristics.The axial end-effect of the ironless PM machine is considered by introducing a correction factor,and the calculation of the EMF accounting for the axial end-effect and end windings is obtained.An experimental prototype is fabricated and the back EMF and inductances are both measured.The effectiveness of the theoretical analysis is validated by experimental results.Finally,the effectiveness of the combined SD model for analyzing the rotatory PMSM is verified by the ironless PM machine.Part III.An arc-linear PMSM used for the low speed direct-drive servo system is designed and analyzed by the combined SD model.The electromagnetic performances are checked and some primary design parameters are readjusted.Part IV.The electromagnetic performances of the ironless,slotless and slotted linear PMSMs are investigated by the proposed combined SD method,respectively.The experimental prototypes of the slotless and slotted linear PMSMs are manufactured,and the effectiveness of the analytical models is validated by the experimental results,such as the detent force,back EMF and static thrust characteristics.The influence of the curvature effects of the inner and outer SD models on the calculation accuracy is researched.The comparisons show that the compressed or stretched curvature effect make the calculation results smaller or larger the theoretical results,while the combined SD model does not suffer from the curvature effect.The computation time between the analytical models and the FEM is also compared.Part V.According to the Maxwell stress tensor,the local magnetic forces in linear PMSM are calculated and the optimal integration surfaces are presented.The slot forces in linear PMSM with different situations of the actual slot number and the effective slot number are researched.If the actual slot number is one more than the effective slot number,the resultant slot force will be mainly dominated by the one end slot force.The electromagnetic coupling between the slot effect and the end effect is investigated,and the results show that the influence of the slot effect on the end forces can be ignored,while the end effect has a relatively larger impact on the slot forces,which will make the slot forces asymmetric.Part VI.The optimization methods for reducing the primary end effect,secondary end effect and slot effect are proposed,respectively.According to the spectrum analysis of the left/right end forces,the optimal primary length is obtained by a two-step iteration,and the step-skewed auxiliary irons are added to eliminate the second order harmonics and reduce other high-order harmonics.The secondary end effect is compensated by adding mirror PMs on the secondary end region.An optimization method with unequal slot-openings is proposed to eliminate the one end slot force and improve the symmetry of all the slot forces.