According to 46 CFR, Subchapter J (Electrical Engineering), emergency generators are required to have specific safety shutdowns, including prime mover over speed. If a direct coupled emergency diesel generator's rated rpm is 1200, what is the maximum setting of the over speed trip device allowed?
• 46 CFR Subchapter J – Electrical Engineering requirements for emergency generator protection • Typical allowable percentage of overspeed for diesel engine emergency generators • How to convert a permitted percent overspeed into an rpm value based on rated speed
• Look up what percentage of rated speed 46 CFR allows for the over speed trip setting on an emergency diesel generator. • Once you know the allowed percentage, multiply it by the rated speed (1200 rpm) to find the maximum allowed trip setting. • Compare your calculated rpm with the choices and pick the one that does not exceed the regulation limit but matches your calculation.
• Verify in 46 CFR Subchapter J the exact maximum percent of rated speed permitted for an overspeed trip on an emergency generator prime mover. • Carefully compute the rpm using: rated rpm × (1 + allowed overspeed percentage). Check your math step by step. • Confirm that the choice you select is at or below the maximum allowed value you calculated, not above it.
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