Electromechanical Relays

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Why Electromechanical Relays?

Separation of AC and DC circuits

Interface between electronic control circuits and power circuits


The Principle Behind Electromechanical Relays


A relay is similar to a switch, it is either open or closed. When the switch is open no current passes through the relay, the circuit is open, and the load that is connected to the relay receives no power. When a relay is closed, the circuit is completed and current passes through the relay and delivers power to the load.

To open and close a relay an electromagnet is used. When the coil controlling the electromagnet is given a voltage, the electromagnet causes the contacts in the relay to connect and transfer current through the relay.



Electromechanical Relays: What’s Inside


This diagram shows the basic parts of an electromechanical relay: a spring, moveable armature, electromagnet, moveable contact, and stationary contact. The spring keeps the two contacts separated until the electromagnet is energized, pulling the two contacts together.

Electromechanical Relay Limitations

The contacts wear and thus have limited life depending on loads
Short contact life when used for rapid switching applications or high loads
Poor performance when switching high inrush currents
Package Size

Conclusion

Electromechanical relays are an excellent solution to separate electronic control circuitry and power circuitry. Electromechanical relays are not the best choice in high frequency switching applications and do have a limited life due to wear on the contacts inside the relay. When used in the a proper application, the electromechanical relay provides safe and reliable integration between power circuits and control circuits.