Design of a foil-wound air-core transformer for fast rise-time pulses

Foil-wound transformers are used in pulsed power applications as pulse transformers. Under fast rise-time pulse conditions, questions are raised concerning the effect of winding non-uniform current distribution on the transformer output wave shape performance. A design process is required to accurately predict the output waveform performance of air-core foil-wound transformers, and to identify the pulse forming network (PFN) design modifications due to the impact of the transformer.;This research describes the design process and transformer representation methods by the development of a non-uniform current distribution transformer model which will predict the fast output pulse performance of a foil-wound transformer. A method was developed to evaluate the true effective air-core turns ratio for the transformer model, and EMTP simulations were effectively used to identify the PFN design modifications. Design criteria were established based on the computer simulations. The transformer foil windings were represented by a mutually coupled network system consisting of narrow filaments. The output waveform of the foil-wound non-uniform current distribution transformer system was predicted using EMTP simulations of the model. A foil-wound pulse transformer was then constructed. Experimental tests were made on the transformer in the Power and Electronics laboratory at the University of Pittsburgh in order to further verify the theoretical model. The simulated output waveforms for both uniform and non-uniform current distribution models are presented as a function of time for the transformer, and results were compared with the measured waveforms. The EMTP non-uniform current distribution model results showed good agreement with the measured results, verifying the validity of the model. Based on the research and EMTP simulations, a complete design strategy was established using the non-uniform current distribution model to predict the waveform performance, fulfilling the given constraints.