A METHOD OF DETERMINING MODES OF CURRENT CONDUCTION IN A CLASS OF AC TO DC CONVERTERS

Abstract

This paper presents method of determining the different modes or aspects of current conduction in ac to dc converters. The phase-controlled converter (with or without current free/fly wheeling) is discussed in detail to show the application of this method. In the discussion, the control delay angle range is limited to radians (which is the half cycle angular distance of the ac source voltage) while the duration of the semi-conductor switch turn on signal is maintained constant throughout the control delay angle range. In the method, continuous load current mode is initially assumed and the instantaneous converter output currents are determined at points of the converter output voltage discontinuities and/or at points of minimum output current values. From the signs of these instantaneous current values, the converter output current modes are identified. The reported method has the advantage of giving more information about the nature/shape of the converter output current waveform and the degree of load current continuity or discontinuity from the transition of continuous to discontinuous current conduction modes.