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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