Induction Motors MCQs
1. An Induction motor is turning at 1200 rpm, the frequency is 60 Hz. The number of poles are:
- 2 poles
- 4 poles
- 6 poles
- 8 poles
Ans: 3
2. The correct statement about the induction motor (IM):
- It requires no dc field current
- It requires only one dc field current
- It requires multiple dc field currents
- None of them is correct
Ans: 1
3. Crawling is a phenomenon associated with squirrel cage design in which IM runs at a very slow speed, this phenomenon occurs due to:
- Low voltage
- Heavy loads connected to rotor
- Bad mechanical design of the machine
- Harmonics
Ans: 4
4. Fractional slip can be expressed by the equation:
- Rotor’s copper loss / Rotor’s input
- Rotor’s copper loss / Rotor’s output
- Stator’s copper loss / Stators input
- Stator’s copper loss / Stators input
Ans: 1
5. A single phase motor is running slower than its original speed, the most obvious case which happened can be:
- Winding is open
- Winding is short
- Bearings are warm
- All are possible
Ans: 3
6. The motor which has high starting torque:
- Squirrel cage induction motor
- Slip ring induction motor
Ans: 2
7. The synchronous speed of a 4 pole machine operated at 50 Hz is:
- 200 r/min
- 1500 r/min
- 10,000 r/min
- 50 r/min
Ans: 2
8. Commonly, the power factor of a single phase induction motor is:
- Leading
- Lagging
- Unity
Ans: 2
9. Which of the following method Starting methods has the lowest starting torque associated with it:
- ATL
- Auto-transformer
- Wye-delta
- All have equal
Ans: 3
10. The statement VFDs never use electronic components is:
- True
- False
Ans: 2