Polyphase Converters for Power Applications

New improvements on the polyphase converter with transistors and saturable cores are presented. Methods to increase the output power and to minimize the weight and volume are discussed. In order to increase the output power, two methods are proposed; one is to insert an additional saturable core in the timing circuit of the converter and the other is to make use of the bridge circuit. The use of the pulsed dc voltage is developed so that the volume of the core may be minimized for the low frequency application. In this case, we find an important phenomenon, i.e. the memory effect of the capacitor, in the transistor base drive circuit. Finally, the problems of controlling the induction motor are discussed. The bridge circuit has valuable characteristics for this application. In this case saturable cores can be removed. A simple method to determine the phase rotation is also proposed.