A fault condition where the fuse or circuit breaker opens due to excess current indicates which primary coil fault?

A fault condition where the fuse or circuit breaker opens due to excess current indicates which primary coil fault?

• A. Faulty Secondary Coil
• B. Derating Factors
• C. Open or Shorted Primary Coil
• D. Resistance Testing

Answer: (C)

The key idea is that overcurrent protection trips when current rises beyond what the circuit can safely carry. A fault in the primary winding that changes its impedance—most commonly a shorted turn in the primary—creates a low-impedance path from the source, causing a surge of current. That surge triggers the fuse or circuit breaker to open to protect the equipment. The option that mentions the primary coil as open or shorted matches this scenario because a fault in the primary winding is what directly leads to excessive current flow and subsequent interruption. A faulty secondary coil tends to affect voltage or loading on the secondary side rather than cause a primary overcurrent condition; derating factors describe environmental or loading considerations rather than a specific fault; resistance testing is a diagnostic method, not a fault condition.

The key idea is that overcurrent protection trips when current rises beyond what the circuit can safely carry. A fault in the primary winding that changes its impedance—most commonly a shorted turn in the primary—creates a low-impedance path from the source, causing a surge of current. That surge triggers the fuse or circuit breaker to open to protect the equipment. The option that mentions the primary coil as open or shorted matches this scenario because a fault in the primary winding is what directly leads to excessive current flow and subsequent interruption. A faulty secondary coil tends to affect voltage or loading on the secondary side rather than cause a primary overcurrent condition; derating factors describe environmental or loading considerations rather than a specific fault; resistance testing is a diagnostic method, not a fault condition.