HVAC · Practice-Exam-2 · Problem 72PDFSolution in PDF ↓
HVAC · Practice-Exam-2 · Problem 72
Problem & Solution
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Topic: Practice Exam #2 — A 460 volt 3 phase AC motor rated for 60 horsepower operates with an efficiency of 93% and a power factor of 0.85.
Method: How much current will the motor draw?
Key values: 60 horsepower
Reference: reference handbook
✅ Answer: C
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Student questions asked in live office hours about this problem
OH 124 · July 6, 2026
Q: Why is motor efficiency included when calculating current draw instead of assuming the motor draws the rated output power?
A: Motor horsepower ratings describe output shaft power, not electrical input power. Because input power must be higher than output power by the efficiency factor, efficiency belongs in the calculation when converting the required output horsepower to electrical current draw.