• Systems Hardware and Components

Field Failure Relay

The Field Failure Relay protects the DC shunt wound motor or main circuit, under open field conditions. (or in the absence of field supply) Speed of the shunt wound DC motor increases as the field supply is weakened. Theoretically, a motor runs at infinite speed if run without field supply. This breaks open the armature coils from the commutator and damages the prime mover. Field failure relay is used in series with the field circuit to ensure that power is not supplied to the armature unless field circuit is complete. This relay is also used as safety guard in DC clutches, solenoids and brakes.