Phase Fault Protection | Induction Motor Protection

Phase Fault Protection | Induction Motor protection

Phase fault protection is nothing but an attracted armature type relay unit is connected in each phase current transformer of the motor. This protection is also called short circuit protection. the current transformer sense the motor current as well the short circuit current. At the time of a fault (short circuit between the phases), the current increases by 5 to 10 times the full load current of the motor. Due to this phase to phase faults can cause burn out of coils and stampings and hence motor should be disconnected as quickly as possible when fault occurs. The high speed tripping over current relays are used to provide phase fault protection.


Phase fault protection
Phase Fault Protection

As mentioned above to avoid relay functioning during starting, the short circuit protection current setting must be just above the maximum starting current of the motor. Modern microprocessor relays come with the instantaneous current protection, which is very much faster than electromagnetic relays.

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