Latching and Non-Latching Relays

 Latching and Non-Latching Relays

Non-Latching Relays

This type of relays is initially at a normally closed (NC) position which is maintained by the force of a spring or magnet if no current flows through the coil. 

If a current starts flowing through the relay coil, the normally open (NO) contact is operated by the magnetic field of the coil and when the current stops, it reverts back to the NC position, as shown in the below figure.

Latching Relay

These relays are used in applications where there is a need to limit power dissipation and consumption. 

These latching relays consist of 1 or 2 coils and have no default position, but when current stops flowing remain in their last position. 

Once these relays are actuated they didn’t require any power to maintain their position, but their reset position is based on the control circuitry. 

The direction of current flow in one coil relay determines the position of the relay, whereas particular coil current flow determines the position of armature in 2–coil latching relay.