Degree Name

Doctor of Philosophy


Department of Electrical and Computer Engineering


This thesis describes the development of a two phase actively clamped resonant DC link inverter (ACRLI) suitable for high performance servo drive applications. The switching behaviour of power bipolar junction transistors (B JTs) in a zero voltage switching environment is investigated. A semiconductor physics representation of the power BJT is used to model the switching behaviour and to describe the charge movement and electric field as the transistor switches. Simulation and experimental results are included leading to a description of the physical behaviour of the power BJTs when used in soft switched circuits. Losses are analysed and found to be minimised when reverse base current is high enough for some current tail to be present. A new model for calculating losses is proposed which is more accurate than those used previously. Improvements to the base drive for soft switching are also discussed.