Magnetic Design of Relays

Abstract

The mechanical work and the speed of operation of telephone relays are determined in a large measure by the characteristics of the relay magnet. The underlying magnetic principles and the resulting design relationships for magnets are discussed in this article, which is in part a review of the background material and in part a description of its use in developing methods for magnet design and the analysis of magnet performance. Basic energy considerations are shown to determine the relations between the work capacity and the magnetization characteristics, and analytical expressions for the latter are given in terms of the dimensions and materials of the magnet. These expressions are developed for the magnetic circuit approximation to static field theory, which is shown to provide an adequate representation of the field relations controlling performance. Methods are given for representing the magnetic circuit relations by means of a simple equivalent circuit. Expressions are derived for the mechanical output of the relay in parameters of this simple equivalent circuit, and these expressions used to determine optimum conditions for meeting specific design objectives.