Selenium power rectifiers for A-C aircraft systems

Increasing electric-power requirements for large aircraft have brought about the introduction of a-c power systems. Two major systems have been developed. In the first power is generated at variable frequency and converted to direct current; in the second power is generated at substantially constant frequency, and both a-c and d-c power are used. In both systems selenium rectifiers can be used as converters. Rectifier units developed to supply 28.5-volt regulated d-c power, which include step-down transformers and voltage-regulating equipment, are described in this paper. Ratings vary from 100 to 800 amperes.