Necessity of relay for electrical motor

1. A relay is a device that opens or closes an auxiliary contact under some predetermined condition in the main circuit.
2. It also provides complete electrical isolation between the control circuit and power circuits.
3. Main parts of relay are armature contacts and coil.
4. it has normally open (NO) contact which can be closed by action of relay. It has normally closed (NC) which can be opened by action of relay.
5. Relay can be operated for 6v, 12v, 18v, 24v, 48v, 110v, DC or AC.
6. When current flows through the coil, the armature is attracted and operates the contact.
7. By one relay several sets of contact may be operated.

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