Application of rectifiers to British Railways a.c. motive power

The paper deals with the various factors which influence the design of rectifier equipments used in the main propulsion power circuits for electric locomotives and multiple unit trains operating on British Railways 50Hz single-phase a.c. system. The special nature of the traction load is described, followed by an outline of the supply system and the fundamental features of the various rectifier circuits with reference to all types of rectifier devices in use, i.e. mercury-arc tanks, and germanium and silicon diodes. The important question of protection against overvoltage and overcurrent is dealt with in some detail, and the various methods of mounting and cooling the equipment are discussed. The paper ends with a survey of the operating experience which has been obtained with the various classes of motive power, highlighting the most attractive characteristics of individual types of equipments as well as those features which have led to modifications and, in some cases, conversion of complete rectifier equipments.