Applied Electrical Engineering Mid - I, September - 2014

1.The frequency of emf generated by an alternator depends upon the alternator speed (N in rpm)and number of poles on the alternator field P and is given as
  • PN/60
  • 60N/p
  • PN/120
  • 120N/p
Answer: C
2.3-phase synchronous motors need---
  • Dc supply only
  • 3-phase ac supply only
  • 3-phase ac supply as well as dc supply
  • 3-phase ac supply and single phase ac supply
Answer: C
3.The doubly excited magnetic systems are
  • solenoids
  • synchronous motors
  • electro-magnetic relays.
  • none of these.
Answer: D
4.A 3-phase synchronous motor needs dc supply for excitation
  • continuously
  • at the starting instant only.
  • of stator
  • none of these.
Answer: A
5.The rotor of an induction motor rotates in the direction of the rotation of stator field in order to—
  • Reduce the relative speed between the rotating stator field and the stationary rotor conductors
  • Oppose the rotor current
  • increase the relative speed between the rotating stator field and the stationary rotor conductors
  • None of the above
Answer: A
6.In modern alternators , the rotating part is
  • field system
  • armature
  • armature as well as field system
  • none of the above
Answer: A
7.A 3-phase transformer ,over a bank of 3-single phase transformers of equal rating ,has the advantage of
  • low cost
  • less weight
  • occupation of less space
  • all of the above
Answer: B
8.Which of the following connection of transformer will give the highest secondary voltage?
  • delta primary, delta secondary
  • delta primary, star secondary
  • star primary, star secondary
  • star primary, delta secondary
Answer: B
9.In star –delta connection the ratio between secondary and primary is-------times the transformation ratio of individual transformers.
  • 1/1.732
  • 1.732
  • 3
  • 1/3.
Answer: A
10.The salient pole type rotors have
  • two or four projecting poles carrying the field coils
  • a large number of projecting poles carrying the field coils.
  • thick steel laminations riveted together and fixed to the rotor by a drove-tail joint
  • all of the above except
Answer: D
11.Turbo generators are consists ------------type of Rotator.
Answer: Cylindrical
12.In star connection the relation between line voltage and phase voltage is----------------
Answer: VL=1.732 V ph
13.In Delta connection the relation between line voltage and phase voltage is -------------------.
Answer: VL=V ph
14.Damper windings are used in which rotor --------------
Answer: Salient type
15.In cylindrical type rotor the airgap is ----------------.
Answer: Uniform
16.The direction of rotation of an induction motor depends upon the------------------
Answer: Phase sequence
17.The winding having larger number of turns will be having ------------induced emf.
Answer: More
18.Synchronous reactance can be defined as sum of ---------------and --------------reactance.
Answer: Leakage flux reactance, reactance of armature reaction
19.For parallel operation , the frequencies of two machines should be-------------
Answer: Same
20.Hydro generators are consists ---------------type of rotor.
Answer: Salient