What Is a Relay Switch Used For?

A relay switch may be used to regulate the flow of current between a circuit and device. Relay switches make it the transfer of current safe, particularly if the circuit and the output device are unable to handle a direct electrical connection.

A relay switch often opens and closes circuits via electromechanical or electronic means. They control one electrical circuit or output device by opening and closing the contacts on another circuit. Relay contacts are identified as normally open (NO) or normally closed (NC). NO contacts are open when they are not energized and NC contacts are closed when they are not energized. However, electric current will change the state of either type of contact.

Relays are able to control the flow of current between when a low-voltage circuit controls a high-voltage circuit. Relays also come in two different forms:

  • Electromechanical
  • Solid state (SSR)

An electromechanical relay (EMR) use magnets to open and close the circuits while solid state (SSR) relays use electronics. Additionally, protective relays help guard against damage within equipment and components through the identification of electrical abnormalities like reverse currents and overloads. Relays are used in a wide variety of applications such as to start heating elements, pilot lights and alarms.