Magnetic Equivalent Circuit Modelling of Synchronous Machines

Design of electric machines constitutes a complex and nonlinear problem where the primary design tool is mainly the finite element method (FEM) in the absence of an accurate and easy to implement analytical technique. Although the accuracy of the FEM is high, its adoption within multi-objective optimization is hindered by the high computational burden. The latter is further exacerbated when more than one operating point needs to be optimized as in traction applications. This paper presents a highly accurate and computationally efficient magnetic equivalent circuit (MEC) model which can be used to design electric machines. MEC model is derived in a general fashion so that any machine can be freely defined with minor geometrical discrepancy. The flux paths are identified based on bi-directional reluctance cells considering material non-linearity. Once solved, it is then possible to obtain all electromagnetic performance indexes such as flux linkages, torque and torque ripple. Accuracy of the MEC model is verified using FEM, showing good agreement between results but obtained in a fraction of time (circa 12 to 20 times faster). The presented modeling approach is then used to perform a sensitivity study focusing on the effects of the discretization and so the trade-off with the computational time.