Wednesday, 8 May 2013


A relay is an electrically operated switch. Many relays use electromagnet to operate a switching mechanism mechanically but other operating principles are also used,

Use of relay:
Relays are used where it is necessary to control the circuit by a low power signal( with complete electrical isolation between control and controlled circuit), or where several circuits must be controlled by one signal.

a type of relay that can handle the high power required to directly control an electric motor or other loads is called a contactor.

Solid state relays control power circuits with no moving parts instead using a semiconductor device to perform switching.

Relays with calibrated operating characteristics and sometimes multiple operating coils are used to protect electrical circuits from overload or faults. in modern electrical power systems these functions are performed by digital instrument still called protective relays.


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