The characteristics and applications of metal rectifiers

Important developments in physical and electrical research, coupled with improvements in manufacturing technique have, during the recent war, considerably improved the characteristics and greatly extended the field of application of metal rectifiers. Of the many types of ‘dry plate’ or ‘barrier layer’ rectifiers developed, the copper oxide and selenium types are by far the most well-known, mainly by reason of the fact that they have proved by far the most successful. The paper is confined mainly to a brief consideration of the characteristics and a more detailed treatment of the applications of the modern selenium-compound rectifier, which has superseded its copper oxide equivalent for industrial and power applications. It is emphasized, however, that the copper oxide rectifier is not by any means obsolete, in that it possesses characteristics which cause it to be selected for use in certain circuits in preference to the selenium type. For this reason, and also in view of the interest shown by engineers in the relative merits of the two types, some space has been devoted to a comparison of characteristics. The uses of the selenium-compound rectifier are now so numerous and diverse that full treatment in a technical paper is not possible. An effort has therefore been made to summarise a large number of typical applications in concise form and in this process much detail has been omitted. The paper concludes with an indication of the lines along which research and development are now proceeding in an effort to further extend the application of the modern barrier-layer rectifier.