HVAC · Practice-Exam-1 · Problem 74PDFSolution in PDF ↓
HVAC · Practice-Exam-1 · Problem 74
Problem & Solution
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Problem: A 3 phase AC generator supplies 700 amps at 480 volts with a power factor of 0.8 and an efficiency of 90%.
Key step: The engine speed is 3600 rpm.
Watch out: So, not all of that electricity will be converted to breakhorse power, so there's some efficiency when we expect to get less out than we put in as wit...
✅ Answer: D
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Student questions asked in live office hours about this problem
OH 99: HVAC: Full Practice Exam #74
Q: So we'll call that W dot, maybe I'll use the subscript, ELEC for electrical, but it's W dot, it's a electrical work. KW would be the units, right?
A: And it's outputting mechanical power, which is to say it's spinning a shaft, and we'll call that horsepower specifically, break horsepower, because it's mechanical power spinning a shaft. We wanted to distinguish that from an AC generator. It's kind of doing the opposite.