The Pacific Journal of Science and Technology –91– http://www.akamaiuniversity.us/PJST.htm Volume 11. Number 2. November 2010 (Fall) Continuous Load Current Mode Analysis of Phase-Controlled AC to DC Converters. C.U. Ogbuka, M.Eng. * and M.U. Agu, Ph.D. Department of Electrical Engineering, University of Nigeria, Nsukka, Nigeria. E-mail: ucogbuka@yahoo.com * drmarcelagu@yahoo.co.uk ABSTRACT In this paper, an insightful analysis of controlled AC to DC converters operating under continuous load current mode is presented. The midpoint converter, as the basic building block of other AC to DC converter application circuits, is first analyzed in positive and negative conversion modes. The full bridge converter, fully controlled, is shown to comprise a positive and negative midpoint converter sharing a common AC input and differentially supplying a common output load. The analysis results can be used to predict the output performance of any standard phase controlled converter application circuit with any given number of AC input phases and/or output pulses under continuous load current. The software for simulation is Ansoft SIMPLORER ® . (Keyword: AC to DC converter, continuous load, current mode, midpoint, full bridge) INTRODUCTION AC to DC converters are widely applied industrially, commercially, and domestically. The AC to DC converter changes AC input voltage/current to an output with unidirectional current. The conversion can be controlled or uncontrolled. When uncontrolled, the switching semiconductor used is the diode. When controlled, the switching semiconductor is the three phase terminal thyristor or transistor. The thyristor is preferred because of the nature of the AC input with which thyristor turn-off can be effected. The AC to DC converter are of two basic configurations: a) The midpoint AC to DC converter b) The full bridge AC to DC converter THE FULLY CONTROLLED MIDPOINT CONVERTERS The fully controlled AC to DC midpoint converters, especially the two and the three pulse types, constitute the primary units for configuring or realizing other forms of AC to DC converters. The midpoint converter has two forms of connection namely: the positive (forward connected) converter and the negative (reverse connected) converter. In phase control, the control parameter is control delay angle whose zero point is given by: ) 1 2 1 ( 0 p N t (1) Where p N is the converter output pulse number and the control signal length for continuous gating is p N 2 . The circuit configurations for two and three pulse midpoint converter configurations are as shown in Figure 1. Figure 1: Two Pulse Midpoint Positive Converter. 1 T 2 T R L E s v s v _ _ 1 g i 2 g i o i o v _ _