Selenium Rectifiers and Their Design

Selenium rectifiers are dry-plate rectifiers of the electronic type. The history of dry rectifiers hegan some 30 years ago with the advent of the copper-sulphide rectifier. In the early 20´ s, the copper-oxide type came into common use, and during the past three years, selenium rectifiers have found wide application in American industry. Fundamentally, this third and latest type of rectifier is a continental development and has been manufactured in Europe within the International Telephone and Telegraph group of companies during most of the 1930´s. Sufficient experience was gained in the technique of manufacture, as well as in methods of design and in selection of applications, to warrant engineering statements as to their general usefulness and importance to industry. The purpose of this paper is to outline general principles of design of stacks, one or more of which make a rectifying unit. Starting with the availability of selenium plates or discs of various types, the engineer is confronted with the problem of 1. Selecting the proper size of plate to provide the required d-c output. 2. Computing the required a-c voltage to be impressed on the rectifier stacks to give the necessary d-c output. 3. Analyzing various factors such as type of load, nature of service, and cost of selected rectifier. The paper includes dynamic and other characteristics of the principal sizes of selenium rectifier plates as applied to the design of single-phase, three-phase, full-wave, and half-wave rectifier units, and all variety of loading.