High voltage ignitron rectifiers and inverters for railroad service

Single-anode pumped-type mercury-arc-rectifier tubes have been established in the 300-, 600-, and 900-volt field in the past few years, and as a result they have become the most important type of equipment for large power conversion at these voltages. The ignitron was the major development which brought about the change from multianode to single anode tubes in this low voltage field.¹ Recently sealed ignitrons have been developed for very high voltages and lower currents.² This paper describes high voltage pumped ignitrons which have been made available for power conversion in the 3,000-to 4,000-volt range. The major application for mercury arc rectifiers in this voltage range is for railroad service. Therefore, the requirements for railroad loading have been given special consideration in the design of the high voltage ignitron. Both rectifier and inverter characteristics were desired in one unit so that a maximum of flexibility could be obtained. The characteristics of combined rectifier and inverter operation are described. Accepted fundamental rectifier and inverter relationships are presented, and curves are included to aid in determining operating characteristics. The design and tests which led to the successful development of the high voltage pumped ignitron are discussed. Pumped ignitrons are compared with sealed ignitrons for high voltage applications so that the field of each can be better defined.