Field-Circuit-Motion Coupled Analysis For Switched Reluctance Motor

Switched reluctance motor (SRM) has been used in many fields in view of its applicability in hard operating environments, high reliability and simple structure. Therefore, SRM has been a choice of driving motor for electric automobile in 863 project of our country. The hot and difficult problems in SRM field have been researched in this thesis.SRM steady-state and dynamic-state performance analysis. The electromagnetic field of SRM is very complicated due to its peculiar double salient configuration and switched controlling circuit although its structure is simple. The SRM is such a kind of complex nonlinear system with local high saturation level, not ignorable couple between phases and flexible control that it is difficult to analyze its performance accurately using conventional method. Firstly, for the computation of 3D flux linkage which is a difficult problem in 3D magnetic field analysis of motors, a computing method combined with mesh reconstruction has been proposed based on 3D FEM analysis. The magnetic field of the end-part of SRM varied with rotor position and phases currents have been analyzed, and the inductance curves of the end part of the windings are obtained.A 2D filed-circuit-motion coupled model that magnetic field FEM equations and controlling circuit equations are coupled directly has been presented to calculate the steady-state performance of SRM under different rotating speed and different controlling mode. And the fault operating state that one of the stator windings breaks from the circuit has been simulated using this model. Introducing the inductances of the winding end parts into the 2D FEM model, the effects of end-part magnetic field for SRM with different configuration and different winding connecting type have been investigated in this thesis.A method of predicting iron core losses in SRM has been presented based on electromagnetic field analysis, in which the iron core losses is estimated by series of components and corresponding frequencies of flux densities in different parts of its iron core. The iron core losses of the SRM operating at different rotating speed are estimated and measured. Concerning the dynamic-state performance analysis involving coupled problem between electromagnetic and mechanical system, the time-stepping FEM model is established to predict the starting characteristics of the SRM.Research and application of force calculating methods. Maxwell stress tensor method, virtual work method and nodal force method have been researched and discussed, and the method to choose a proper integrating path in 2D Maxwell stress method is proposed upon theoretical and numerical demonstration. Furthermore, the variation of the force acting among stator and rotor poles of SRM with rotor rotation has been analyzed using the nodal force method, and the nodal force method has been simplified to decrease computation cost with the same accuracy.Influence of controlling parameters on vibration of SRM. The vibration and noiseproblem of the SRM is more serious than other motors, which is caused by two main factors, the torque ripple and the radial force acting on stator poles. Therefore, analyzing these two factors quantitatively is significant to decrease the vibration of SRM. The torque ripple and the radial force of SRM on the same steady-state operating point but different switch-on and switch-off angles have been computed numerically in this thesis, and the corresponding vibration waveforms and spectrums for different controlling angles have been tested respectively. Based on these researches, the influence of switch-on and switch-off angle on SRM vibration has been investigated through the analysis of torque ripple and radial force.