Practice Test: Question Set - 07
1. The speed of a squirrel-cage induction motor can be controlled by all of the following except
- (A) Changing supply frequency
- (B) Changing number of poles
- (C) Changing winding resistance
- (D) Reducing supply voltage
2. The auto-starters (using three auto transformers) can be used to start cage induction motor of the following type
- (A) Star connected only
- (B) Delta connected only
- (C) Both (A) and (B)
- (D) None of the above
3. In Ns is the synchronous speed and s the slip, then actual running speed of an induction motor will be
- (A) NS
- (B) s.N
- (C) (l-s) Ns
- (D) (Ns-l) s
4. When the equivalent circuit diagram of double squirrel-cage induction motor is constructed the two cages can be considered
- (A) In series
- (B) In parallel
- (C) In series-parallel
- (D) In parallel with stator
5. The shaft of an induction motor is made of
- (A) Stiff
- (B) Flexible
- (C) Hollow
- (D) Any of the above
6. Low voltage at motor terminals is due to
- (A) Inadequate motor wiring
- (B) Poorly regulated power supply
- (C) Any one of the above
- (D) None of the above
7. A 500 kW, 3-phase, 440 volts, 50 Hz, A.C. induction motor has a speed of 960 r.p.m. on full load. The machine has 6-poles. The slip of the machine will be
- (A) 0.01
- (B) 0.02
- (C) 0.03
- (D) 0.04
8. In a squirrel cage motor the induced e.m.f. is
- (A) Dependent on the shaft loading
- (B) Dependent on the number of slots
- (C) Slip times the stand still e.m.f. induced in
the rotor
- (D) None of the above
9. In an induction motor, no-load the slip is generally
- (A) Less than 1 %
- (B) 1.5 %
- (C) 2 %
- (D) 4 %
10. An induction motor with 1000 r.p.m. speed will have
- (A) 8 poles
- (B) 6 poles
- (C) 4 poles
- (D) 2 poles
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