USCG Exam PracticeElectrical basics — generators, motors, and safety
A shipboard AC generator nameplate shows a full load rating of 200 amperes. The overcurrent device protecting this generator is currently set at 240 amperes. Which statement correctly evaluates this installation under applicable federal regulations?
- A. The setting is compliant because 240 amperes is within 125 percent of the full load rating
- ✓ The setting is non-compliant because it exceeds 115 percent of the full load rating, which equals 230 amperesCorrect
- C. The setting is compliant because the regulation only applies to DC generators
- D. The setting is non-compliant because the overcurrent device must be set at exactly 100 percent of the full load rating
Why B is correct
46 CFR §183.320(f) requires the overcurrent device to be set at a value not exceeding 115 percent of the generator full load rating. For a 200-ampere generator, 115 percent equals 230 amperes. A setting of 240 amperes exceeds this limit and is therefore non-compliant. The 125 percent figure does not appear in this regulatory provision, and the rule applies to generators generally, not only DC machines.
Cited:46 CFR §183.320