Electromechanical Relays

Relays are switches that open and close circuits. They control one electrical circuit by opening or closing contacts in another circuit. When a relay contact is normally open (NO), there is an open contact when the relay is not energized. When a relay contact is normally closed (NC), there is a closed contact when the relay is not energized. Applying electrical current to the contacts will change their state. Many relays use an electromagnet to mechanically operate a switch, but other operating principles such as solid-state relays are also used. Relays are used where it is necessary to control a circuit by a low-power signal or where several circuits must be controlled by one signal. Depending on the structural features and operating principle, relays are of different types such as monitoring, regulating, auxiliary and protective. Classification of the types of relays depend on the function for which they are used. 

Electromechanical relays transfer signals between its contacts through a mechanical movement. They are made of a coil, an armature mechanism and electrical contacts. When the coil is energized, the induced magnetic field moves the armature that opens and closes the contacts. Electromechanical relays are remote controlled switches capable of switching many circuits, either individually or in sequence. They have high reliability, low power consumption and a long switching operational life. Electromechanical relays are preferred for harsh environments. They are tolerant of high temperatures and perform well in areas prone to electromagnetic interference (EMI) and radio frequency interference (RFI). Surges, transients and noise do not affect an electromechanical protective relay.