A thermal-magnetic circuit breaker for a 300 KW alternator is rated at 500 amperes at full continuous load. Which of the following conditions will trip the breaker?
Official USCG Answer & Rule Citation
Correct Answer: Option C — Instantaneous current draw of 5,000 amperes.
Thermal-magnetic breakers feature instantaneous magnetic trip elements calibrated to react immediately to high fault currents. An instantaneous draw of 5,000 amperes vastly exceeds the magnetic trip threshold of a 500-ampere marine breaker, forcing an immediate trip.
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