Magnetic Latching Relays Using Glass-Sealed Contacts

Latching relays or lock-up relays, as tliey are sometimes called, are becoming important and very useful as switching elements. As a broad definition, a latching or lock-up relay is one whose contacts will remain in the operated state by means of mechanical or magnetic locking or because of reduced energy furnished to the coil or to a separate winding of the coil through a set of auxiliary contacts. Latching relays take several forms, and some similarities and differences in the characteristics of this family of relays will be described. These relays are usually polar. Their most important characteristic is that they are sensitive, and therefore the relays are usually used where power is at a premium or must be conserved. Since they normally are pulse-operated, much power can be saved when a long period of operation of the relay in its operated state is required. Many designs of typical armature-operated relays fall into the latching or locking classification of relay. This paper, however, will deal only with magnetic latching types of relays using glass-sealed contacts.