Abstract :
The paper establishes theoretical formulae for the predetermination of the mean d.c. voltage of a 6-phase gridcontrolled mercury-arc rectifier at large ignition angles. The formulae apply to all loads, from the highly inductive to the essentially non-inductive, and include all essential factors. An experimental investigation gives satisfactory evidence of their validity. This fuller theory proves that, strictly speaking, it is incorrect, in non-overlap cases, to allow for arc-drop by arithmetic subtraction. A selection of oscillograms is included which show smaller ignition angles than those generally accepted (a) for arc extinction, and (b) for the limiting angle between overlap and non-overlap on non-inductive loads.
