Estimation and Control of the Operate Time of Relays: Part II - Design of Optimum Windings

T h e selection of a relay for a circuit application, particularly so in common control systems, involves in p a r t a determination of its operating and releasing time. In P a r t I of this article expressions are derived for t h e relations between these times, t h e design p a r a m e t e r s of a relay, a n d t h e conditions of operation. These expressions are a p p r o x i m a t e , a n d h a v e been developed with p r i m a r y reference to t h e selection of favorable characteristics in design. T h e t i m i n g estimates t h e y provide are of sufficient accuracy for t h e comparison of design alternatives. Once a basic design h a s been selected, t h e choice of windings and t h e prediction of t h e limiting times occurring in specific applications requires 144 ESTIMATION* AND CONTROL OF OPERATE TIME OF RELAYS 159 a more detailed and exact procedure than can he obtained entirely from the application of these approximate relations. The information furthermore has to be quite versatile, to permit all new type variations to be included, such as winding, number of contacts and armature travel. It must, moreover, be in a form t h a t permits determination of the upper and lower limits to the time observed in each specific type of relay as actually used, as in applications, interest attaches not only to the nominal conditions, b u t to all variations t h a t m a y arise in actual manufacture and use. Relay operation is complex, and in principle the nonlinear differential equations which describe it can be solved exactly only by computers.