USCG Exam PracticeMotors and generators
A generator rated for 40 °C ambient is installed in an engine room space where ambient temperature reaches 50 °C. Under 46 CFR §183.320, what corrective measure is required?
- A. The generator must be replaced with one rated for 50 °C; no derating is permitted
- ✓ The generator must be derated to 80 percent of full-load rating and overcurrent devices reduced accordinglyCorrect
- C. The generator must be derated to 90 percent of full-load rating with no change to overcurrent devices
- D. Additional ventilation must be provided so the space temperature does not exceed 45 °C
Why B is correct
46 CFR §183.320(b)(2) permits a 40 °C-rated generator to be used in a 50 °C ambient location only if it is derated to 80 percent of its full-load rating and the rating or setting of the overcurrent devices is reduced accordingly.
Cited:46 CFR §183.320