Date of Graduation


Document Type


Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level



Electrical Engineering


Yue Zhao

Committee Member

Juan C. Balda

Second Committee Member

David Huitink

Third Committee Member

Roy McCann


electric vehicles, busbar, heavy equipment, motor drive, performance, MOSFET, high-power inverter, traction converters


Transportation electrification is clearly the road toward the future. Compared to internal combustion engine, the electrified vehicle has less carbon-dioxide emission, less maintenance costs and less operation costs. It also offers higher efficiency and safety margin. More importantly, it relieves human’s dependence on conventional fossil energy. In the electrification progress, the revolution of electric traction drive systems is one of the most important milestone. The traction system should keep high efficiency to avoid performance reduction. Moreover, the motor drive should be designed within limited space without sacrificing output power rating. Based on the road map from US Drive Electrical and Electronics Technical Team, US Department of Energy, a gap is still there between roadmap target and the state-of-art. To fill the gap, this dissertation performs a systematic research in motor drive system for traction inverters. This paper starts from optimal theoretical design of power converters by using loss model and real-time simulation system. Based on optimal paper design, hardware design is implemented. The component design for converter, such as the laminated busbar, are the focus in this dissertation. The optimized busbar structure can effectively reduce stray inductance in the current-commutation loop, reducing switching overshoots of power modules and increasing semiconductor reliability. The system-level design and trade-off is also analyzed and illustrated by using a 250kW three-level T-type neutral-point clamped converter. The design has reached high efficiency and high-power density. The converter system is also evaluated through comprehensive tests, such as double-pulse tests and continuous tests. The test setup, test condition and test result analysis are discussed in the dissertation. In the end, the dissertation also proposed an improved impedance characterization method for components parasitic inductance measurement in traction drive systems, such as laminated busbar, power module and capacitors. The characterization shares better accuracy and can be customized for device under test with any geometry.