2020 Volume 9 Issue 5 Pages 607-617
The theory for three types of power conversion is established. In a controlled rectifier circuit, the input poly-phase AC sources are switched and connected to the load one by one; thus, AC-DC conversion is established. This mechanism is referred to as power conversion by change of sources. On the other hand, in a DC-DC step-up chopper circuit, there is an interval when the input source supplies energy to a reactor and this reactor energy possessing its own direction is defined as electromagnetic momentum. After a switching action, in the next interval, the circuit begins to enclose the load and forms a current loop circulating through the source, reactor and load. Then, the electromagnetic momentum will force the current to flow into the load which is at a higher voltage than the source. The switch action will be repeated on and off, and the current loop will be changed accordingly; then, power conversion will be established and this mechanism is named as power conversion by change of loops. In addition, by using a four-quadrant switching device to change the source polarity, DC-AC conversion can be achieved, and this mechanism is defined as combined power conversion. Extensive discussions on the technical terms have also been undertaken, such as classification naming for the diode and the thyristor.
