A motor delivers 10 hp at its shaft. What is its output power in watts? (1 hp = 746 W)
Answer in W.
Show the answer
7460 W
Output = hp × 746 = 10 × 746 = 7,460 W.
Reference: Unit conversion: 1 hp = 746 W
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Motors misc practice questions
25 questions from the electrical theory and calculations practice test.
Motors misc practice test
10 questions, graded as you go, with the reason for every answer. No sign-up.
What this covers
- Horsepower and watts
- Motor current
- Synchronous speed and slip
- Motor types
- Voltage drop
- Conductor resistance
- Temperature and unit conversions
Sample questions
What is the synchronous speed of a 6-pole motor operating on 60 Hz?
Answer in rpm.
Show the answer
1200 rpm
Ns = 120 × f ÷ P = 120 × 60 ÷ 6 = 7,200 ÷ 6 = 1,200 rpm.
Reference: Synchronous speed: Ns = 120 × f ÷ P
A 4-pole, 60 Hz induction motor runs at 1,740 rpm at full load. What is its slip in percent?
Answer in %.
Show the answer
3.33 %
Ns = 120 × 60 ÷ 4 = 1,800 rpm. Slip = (Ns − N) ÷ Ns × 100 = (1,800 − 1,740) ÷ 1,800 × 100 = 60 ÷ 1,800 × 100 = 3.33%.
Reference: Slip: s = (Ns − N) ÷ Ns