ABSTRACT

A relay is an electrical component designed to open or close an electrical circuit as the result of an input voltage. Several different types of relays are in use today.

Electromechanical relays require an input voltage and current to open and close the circuit. Typically, an electromagnetic relay has a spring-loaded armature that places the relay in its default position (open or closed). When the input voltage exceeds the relay’s required level to energize, the armature of the solenoid is moved by means of a magnetic field generated by an internal inductor. This movement places the armature in the opposite position (closed or open) until the energizing voltage and current are removed. Electromechanical relays are often used in high-voltage environments. Electromechanical relays may cause sparks or arcing as the high-voltage circuit opens or closes. An audible click or other noise is often heard as the relay armature actuates, and the armature magnetic coil radiates a magnetic field while energized. Electromechanical relays are temperature responsive and may alter operation if a temperature threshold is exceeded. In general, electromechanical relays have a low speed of operation and may cause a “bounce” phenomenon. This bounce is a state induced by arcing as the switch closes or opens, which may appear as several openand-close cycles to the connected system.