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FIELD FAILURE RELAY, also
known as FIELD LOSS RELAY protects the DC Shunt wound
motor or main circuit, under open field conditions,
or in the absence of the field supply
Speed of the Shunt Wound DC Motor
increases as the field supply is weakened Theoretically
motor runs at infinite speed if run without field
supply. This break opens the armature coils from the
commutator and totally damages the prime mover.
The FIELD FAILURE
RELAY, when used in series with the field circuit,
ensures that no power is supplied to the armature
unless field circuit is complete.
FIELD FAILURE RELAY
is a truly current operated device. As there is no iron
core, there is no magnetic storage
and actuating time is less than 1.2 milliseconds
This is also used as safety guard in
DC clutches, solenoids and brakes.
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FIELD FAILURE RELAYS
