Electrical Machines Questions and Answers – Flux and MMF Phasors and Waves in Induction Motors

This set of Electrical Machines Questions and Answers for Campus interviews focuses on “Flux and MMF Phasors and Waves in Induction Motors”.

1. A three phase induction motor is not self starting.
a) True
b) False
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2. Mark the correct waveform for the emf produced in an induction motor and the resultant flux density wave for a resistive load.
a)
b)
c)
d)
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3. Mark the most appropriate phasor for the induction machine operation as motor.
a)
b)
c)
d) none of the mentioned
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4. In a three phase induction motor, rotor current in each phase lags behind the generated emf in that phase to rotor by a power factor angle of _________
a) atan(r2/x2)
b) atan(x2/r2)
c) atan(x1/r1)
d) atan(r1/x1)
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5. In a three phase induction motor of rotor impedance as (0.2+j0.2), rotor current in each phase lags behind the generated emf in that phase to rotor by a power factor angle of _________
a) 45°
b) 135°
c) 90°
d) 0°
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6. For the three phase induction motor having leakage impedance, the maximum generated emf would be attained at an angle of θ having a purely resistive load is?
a) 90 + θ
b) θ
c) 90 – θ
d) -θ
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7. For a slip ring induction motor having leakage impedance of (1+j), the maximum generated emf would be attained at _________
a) 135°
b) 45°
c) -45°
d) 0°
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8. In an induction motor, the stator is also known as _________ and the rotor as __________
a) field winding, armature winding
b) armature winding, field winding
c) armature winding, compensating winding
d) armature winding, interpole winding
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9. For a 6-pole three phase squirrel cage induction motor has flux density wave of four poless, then the rotor induced poles will be?
a) 4
b) 6
c) 2
d) 10
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10. The external resistance can be inserted in rotor circuit of _________
a) wound rotor induction motor
b) slip ring induction motor
c) wound rotor as slip ring induction motor
d) neither of motors
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11. Starting torque induced in a three phase induction motor in a direction of rotating magnetic field depends on _________
a) number of poles squared
b) inverse of number of poles
c) number of poles
d) number of number poles cubic
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12. Starting torque induced in a three phase induction motor in a direction of rotating magnetic field depends on _________

(i) rotor mmf per pole
(ii) rotor power factor angle
(iii)type of rotor winding

a) (i), (ii)
b) (ii), (iii)
c) (i), (iii)
d) (i), (ii), (iii)
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Sanfoundry Global Education & Learning Series – Electrical Machines.

To practice all areas of Electrical Machines for Campus Interviews, here is complete set of 1000+ Multiple Choice Questions and Answers.