Approaches for Improving Overall System Efficiency in Wound Field Synchronous Machine Drives used for EV Propulsion

Date of Award


Publication Type


Degree Name



Electrical and Computer Engineering


Control, Efficiency, Electric vehicle, Wound field synchronous Machine







Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.


In recent years, electric vehicle technologies have evolved rapidly, speeding the transition from internal combustion engine (ICE) vehicles to electric vehicles (EV). With the exponential growth in electric vehicle sales, demand for electric powertrains with higher torque density, higher drive cycle system efficiency, and lower cost has increased. Such a powertrain should lead to increased efficiency, safety, maximum speed, affordability, and driving range of EVs. Addressing these targets, the wound field synchronous machine (WFSM) based powertrain has proven to be a potential candidate for propelling EVs.

Since the WFSM needs a separate rotor excitation system, an inductive power transfer system or a conductive power transfer system using brushes and slip rings could be used. The inductive power transfer (IPT) rotor excitation system has increased loss than the conventional conductive brushed rotor excitation system because of its topology. Therefore, this thesis proposes a maximum overall system efficiency per ampere control for IPT-based WFSMs. The proposed control algorithm improves the overall efficiency by considering WFSM, stator three-phase inverter, and rotor IPT converter losses. The proposed control algorithm is implemented using a proportional-integral controller, and the closed-loop controls are experimentally validated.

This thesis also proposes a novel converter and control topologies for a doubly excited wound field synchronous machine for improving efficiency at lower speeds and torque loads. In the end, an Overall performance comparison between the proposed topologies and finite element analysis simulations for the proposed models are presented.