Relay Accessories

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.

Solid-state relays have no moving parts like electromechanical relays, but utilize electrical components and optical properties of solid-state semi-conductors to perform IO switching functions and isolation. They are designed for applications that require high switching speed without arcing or contact noise. They are highly resistant to vibration and shock and are unaffected by the presence of dust, gases or other contaminants. Solid state relays are used in heating control applications for a compressor’s soft-start, fan, blower, heater and valve control. They are used in lighting applications for dimming and for their ability to operate silently and switch quickly. Because of their resistance to shock and vibration and non-arcing, motion control applications such as lifts, hoists conveyor systems and elevators are the perfect fit for solid state relays.