An FEA/MATLAB based machine design tool for switched reluctance motors

Abstract

Switched reluctance machine (SRM) has a simple and low cost construction owing to the concentrated windings on the stator, no permanent magnets or windings on the rotor. This rugged structure offers many advantages such as high speed, fault tolerant and reliable operation, wide constant power range, low inertia and low inrush currents. However, due to the single source of excitation and dependence of inductance profile on excitation current and rotor position, the mathematical model of SRM is highly nonlinear. Moreover, unlike many other electrical machines, the energy conversion capacity of SRM is greater when working under high magnetic flux densities. In case of SRM with higher number of rotor poles, stator and rotor pole arc angles are limited due to the smaller interpolar gap. Therefore, it's harder to adjust the dimensions of the machine to prevent high saturation at the poles. Considering the nonlinear behavior and design challenges with the higher number of rotor poles, an iterative process is necessary for an SRM design and finite element analysis (FEA) software are widely used to get the inductance and torque profile for the given dimensions. The performance of an SRM is also dependent on torque ripples, which is a function of turn-on and turn-off angles. These parameters cannot be calculated in FEA, because it requires the dynamic control of the phase currents according to rotor position. This paper proposes a MATLAB based design tool, which, for the given machine dimensions and parameters, calculates the geometry and automatically draws and simulates the machine model in FEA software. Moreover using those results, it performs a dynamic simulation in Simulink plots the load torque and phase current profiles and so manages the whole design process. The geometrical and electrical design equations are given and the graphical user interfaces of the design tool are introduced.