Improved model of saturated regions in Magnetic Equivalent Circuits of highly saturated electromagnetic devices

In the magnetic equivalent circuit (MEC) method, a set of lumped permeance elements is used to model the nonlinear magnetic field in electromagnetic devices. The accuracy of the method depends on the geometric shape and size of flux tubes associated with permeance elements as well as the number of elements, particularly for modeling highly saturated regions. Although it is possible to suggest nearly correct graphical shape of tubes in these regions, the actual cross section of such flux tubes is difficult to determine. This paper examines the problem and presents a technique, here called flux ratio criterion (FRC), which is helpful to determine the cross section of each flux tube in highly saturated regions during the solution process of nonlinear equations of the magnetic circuit The proposed technique is used to predict the static characteristics and dynamic performance of a switched reluctance machine (SRM). The results are compared to those obtained from measurement, conventional MEC and FE methods. As a conclusion, the most accurate results are achieved by proper choice of number of elements discretizing the flux into several flux tubes as well as connecting adequate number of elements of proper cross sections in series in highly saturated regions.