Voltage Control by Means of Power Thyristors

This paper is presented as a tutorial informative survey on the subject of voltage control. Voltage control is discussed from several viewpoints: 1) control of direct voltage from an ac source, 2) control of alternating voltage from an ac source, 3) control of direct voltage from a dc source, and 4) control of alternating voltage from a dc source. Such various control modes as 1) phase control, 2) switching control, 3) pulse burst modulation control, and 4) chopper control are discussed. Many circuit possibilities are tabulated together with typical transfer characteristics and notes concerning optimum matching of application and circuit. Also discussed are such allied control subjects as 1) the function of free-wheeling diodes, 2) interphase transformers, 3) power factor effects, 4) capacitive and counter-EMF loads, 5) firing-pulse requirements, and 6) zero voltage switching. Comprehensive listings of circuits and control and application methods are included. These are sufficiently complete to suggest to those skilled in rectifier art other variations which may be useful in solving specific problems.