Electro Magnetic Relay

Electro Magnetic Relay

These relays are constructed from electrical, mechanical and magnetic components, and possess operating coil and mechanical contacts. 

Therefore, when a coil gets activated by a power supply source, these mechanical contacts get opened or closed. 

The type of supply can be AC or DC.

Both AC and DC relays work on the same principle as that of electromagnetic induction,

But the construction is somewhat differentiated and also depends on the application for which these relays are selected. 

DC relays are employed with a freewheeling diode to deenergize the coil, and the AC relays use laminated cores to prevent eddy current losses.

The very interesting aspect of an AC is that, for every half cycle, the direction of the current supply changes.

Therefore, for every cycle, the coil loses its magnetism since the zero current in every half cycle makes the relay continuously make and break the circuit. 

So  to prevent this – additionally one shaded coil or other electronic circuit is placed in the AC relay to provide magnetism in the zero current position.