Design of a WFSM for an Electric Vehicle Based on a Nonlinear Magnetic Equivalent Circuit

This paper presents a design principle of a wound field synchronous motor (WFSM). Because the main flux path is sensitive to magnetic saturation, the WFSM has to be designed considering the latter, especially for applications requiring high torque density such as electric vehicles (EVs). Thus, a magnetic equivalent circuit (MEC) should be constructed considering the nonlinearity of the electrical steel sheets. A nonlinear MEC for the WFSM is constructed and solved by the Newton-Raphson method. Then, using the nonlinear MEC, the design of a WFSM is presented under some given constraints. The result of the final model for an EV is compared to finite-element analysis to verify its accuracy, and experiments on the final designed model are performed.