Alternator MCQ

1.Alternator operates on the principles of

  • AElectromagnetic induction
  • BSelf-induction
  • CMutual induction
  • DSelf or mutual induction
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Answer:

Electromagnetic induction

Explanation:

2.In a synchronous machine, if the field flux axis is ahead of the armature field axis in the direction of rotation, the machine operating is

  • ASynchronous motor
  • BSynchronous generator
  • CAsynchronous motor
  • DAsynchronous generator
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Answer:

Synchronous generator

Explanation:

3.The armature of an alternator

  • Ais a stationary member
  • Bis a revolving member
  • Cis the frame
  • DConsists of the winding into which current is induced
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Answer:

Consists of the winding into which current is induced

Explanation:

4.In modern alternators, the rotating part is

  • AField system
  • BArmature
  • CArmature as well as field system
  • DNone of the above
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Answer:

Field system

Explanation:

5.The current from the stator of an alternator is taken output the external load circuit through

  • ASlip rings
  • BCommutator segments
  • CSolid connections
  • DCarbon brushes
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Answer:

Solid connections

Explanation:

6.Which one of the following is the primary reason for placing field on rotor in an alternator?

  • ASmall power in the filed circuit
  • BInsulation of high voltage is made easy on stator than on rotor
  • CLarge power in stator
  • DLarge current in stator
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Answer:

Insulation of high voltage is made easy on stator than on rotor

Explanation:

7.Which type of alternator is used in hydroelectric power stations?

  • ANon salient pole alternator
  • BTurbo generator
  • CSalient pole alternator
  • DSteam turbine alternator
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Answer:

Salient pole alternator

Explanation:

8.In a synchronous machine, the stator frame serves the purpose of 

  • AHolding the armature stampings in position and also in some cases for circulating cold water for cooling
  • BInsulating the armature windings
  • CProviding path to the magnetic flux
  • DProtecting the whole machine
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Answer:

Holding the armature stampings in position and also in some cases for circulating cold water for cooling

Explanation:

9.In a synchronous machine, the stator frame is made of 

  • AStainless steel
  • BCRGOS
  • CCast iron or welded steel plates
  • DLaminated silicon steel
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Answer:

Cast iron or welded steel plates

Explanation:

10.The stator core of a synchronous machine is built up of ___laminations.

  • AStainless steel
  • BSilicon steel
  • CCast iron
  • DCast steel
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Answer:

Silicon steel

Explanation:

11.The stator core stampings also have opening which make____ ventilating ducts to provide efficient cooling.

  • AAxial
  • BRadial
  • Cradial as well as radial
  • DNone of the above
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Answer:

radial as well as radial

Explanation:

12.The open slots are more commonly used in the stator of a synchronous machine as

  • AThe inductance of the winding is less
  • BThey permit the placement of form wound and insulated coils giving least expensive and more satisfactory
  • CBoth (a) and (b)
  • DNone of these
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Answer:

Both (a) and (b)

Explanation:

13.The field system of an alternator is usually excited at

  • A250/ 250 V DC
  • B110 / 220 V AC
  • C3-phase, 50 Hz 400 V
  • D230V AC
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Answer:

250/ 250 V DC

Explanation:

14.The slip rings employed in a 3 phase synchronous machines are insulated for

  • AOutput rated voltage
  • BLow voltage
  • CVery low voltage
  • DVery high voltage
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Answer:

Low voltage

Explanation:

15.Squirrel cage bars placed in the rotor pole faces of an alternator help reducing hunting

  • AAbove synchronous speed only
  • BBelow synchronous speed only
  • CAbove and below synchronous speeds both
  • DNone of the above
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Answer:

Above and below synchronous speeds both

Explanation:

16.Hydro generators are generally employed to run at ___rpm

  • A500
  • B1000
  • C1500
  • D3000
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Answer:

500

Explanation:

17.In case of turbo alternator, rotor is made of

  • AForged steel
  • BCast iron
  • CStainless steel
  • DLaminated silicon steel
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Answer:

Forged steel

Explanation:

18.The salient pole rotors have

  • AA large number of projecting poles carrying the filed coils
  • BThick steel laminations riveted together and fixed to the rotor by a dove tail joint
  • CPole faces usually provided with slots for damper windings
  • DAll of the above
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Answer:

All of the above

Explanation:

19.In salient pole field structure, the pole shoes cover about ___of pole pitch.

  • AOne third
  • BOne half
  • CTwo third
  • DWhole
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Answer:

Two third

Explanation:

20.Larger diameter salient pole rotors have shorter axial length because

  • Ait occupies much less space
  • Bif saves lot of copper in stator winding
  • Cit reduces weight of the rotor
  • Dnumber of conductors held in large circumference of rotor is very large and so they need not long
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Answer:

number of conductors held in large circumference of rotor is very large and so they need not long

Explanation: