Polyphase Induction Motors MCQ Practice - Set 07 - ObjectiveBooks

# 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
(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
(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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