Improved Design-Oriented Analytical Model for Switched Reluctance Machines' Unsaturated Inductance in Non-Overlap Conditions

Design-oriented analytical modelling of switched reluctance machines (SRMs) is currently an active field of research, as it significantly alleviates the computational burden of design processes by replacing or complementing finite element analysis. The modelling of saturated SRMs, including the determination of saturated flux loci and the calculation of torque and current waveforms, requires prior knowledge of the unsaturated inductance vs rotor position profile. This work proposes an improved analytical model to determine unsaturated inductances in non-overlap conditions, based on a twofold improvement of the permeance method: the use of elliptic flux tubes; and the ability to self-tailor the flux tube shapes to any machine geometry. Its accuracy is proven against finite element analysis applied to four designs and against experimental results of a full-scale prototype. Finally, it is shown how the model can be incorporated into a fully analytical design tool, whose accuracy in calculating performance and computational burden are evaluated.