Solid State Relay vs. Electromechanical Relay

A relay is nothing but an electrically operated switch. To switch power on and off, a relay requires a low power electrical signal. Therefore, a relay is an automatically operated switch that uses low power electrical signal to control a high power electrical signal.

Electromechanical Relay (EMR)

As the name implies, an electromechanical relay is one that uses physically moving contact to control the flow of power in the output circuit. The movement of moving contact is generated using electromagnetic forces created by a low power input signal to the relay, which allowing the completion of the circuit that contains high power electrical signal.

Solid State Relay (SSR)

The solid state relays consist of semiconductor mechanism instead of an electromagnetic system. A low power electrical signal is used to generate optical signal within an optocoupler, which transmits and energizes the output circuit. When the relay is activated, the optocoupler acts as the switch that allows the high power signal to pass through the output circuit of the SSR. Therefore, a solid state relay does not contain any physically moving contacts for their operation.

Difference between Electromechanical Relay and Solid State Relay