| The aim of this research is to design a new polyphase ac-dc converter topology. The new design differs from classical topologies in that, the power transformer is made of a cascade of transformers or alternatively of transformers with an odd number of phases in the secondary windings.;The main benefit of the new converters is that, with a suitable arrangement of the windings of the power transformer, an even current and voltage distribution in the power semiconductors can be achieved. Thus the new converters are specially suited for high voltage or high current industrial applications.;The first stage of the research was the design and simulation of a high voltage dc power supply (70 kV, 60 A). It featured a cascade of three dry type transformers. It behaved like a 36 phase ac-dc converter. It is used to power a high frequency klystron generator at the Canadian Center for Magnetic Fusion at Varennes, Quebec.;In the second stage of the research, a new family of ac-dc converter featuring five and seven phases in the secondary was designed. A detailed analysis of the different configurations of the five phase and seven phase transformers was performed. The converters were simulated and the results checked against test results. It can be concluded that this type of converter can reduce the harmonic contents of the output voltage like their even phase equivalents (6, 12, ... phases). But, and this is their main benefit, they inject far less current harmonics in the supply side (ac network).;As a conclusion, this research heralds the use of a new generation of power transformers. |
