Advanced inverter drives for traction

This paper describes traction propulsion inverters as used in two important applications of such drives in the UK. The drives for the Networker EMU and Eurostar power car supplied by GEC Alsthom Traction are detailed. The difference in technology for these two inverters which operate at power levels of 350 kVA and 1 MVA is emphasised. By comparing the snubber and device losses for these and a higher powered inverter rated at 2.5 MVA, the benefits of low loss and energy recovery snubber designs for high powered traction inverters are explained. The paper also explains how the choice of PWM waveforms can greatly affect the peak device current, thus affecting the maximum junction temperature of the GTOs used. Improvements that can be made in this area are described, including the smooth transition to quasi-square wave operation. Finally, harmonic results from a typical traction inverter are presented, showing how such inverters can be designed to comply with strict signalling specifications