Factors affecting the design of D-C magnets

This paper outlines some of the factors which should be considered in the design of d-c magnets. The usual types of steel used are briefly discussed, including their influence on “sticking” or residual forces. Calculated curves are presented which show the influence of pole-face area on the force developed by the magnet. Flux measurements on a number of magnets show that theoretical calculations are often in great error because of factors such as leakage and saturation which are usually neglected. Data show that the flux in a d-c magnet with a small air gap may vary by as much as 300 per cent between one part of the circuit and another.