Licentiate Thesis Defense-Torbjörn Trosten

Abstract:

The purpose of this licentiate thesis is to research a few key concepts which are important in the development of high efficiency electric drives. The selected research method is quantitative, the raw data have been collected from real world measurements, both from power lab and from train. 

The data is analysed and the results are presented in the thesis and associated papers. The paper in this thesis describes and evaluates the impact of SiC MOSFET inverters on the traction drive. Furthermore, the papers go into depth about losses within the traction drive and how the electromagnetic noise depends on both the inverter switching frequency and pulse width modulation method. In the papers, results from low fidelity models of both losses and noise are presented, these models offer greater insight into the mechanism behind both losses and electromagnetic noise. Understanding how the motor harmonic losses depends on the current distribution in conductors, can contribute to improved designs of both motors and inverters. 

An understanding of how electromagnetic noise increases when voltage harmonics coincide with the mechanical modes of resonance of the electric motor, can further contribute to improved designs of both inverters and motors.

The thesis concludes that when SiC based MOSFETs inverters makes its debut into everyday trains, we can expect significant increases in energy efficiency as well as significantly reductions in electromagnetic noise.