Alternators

#1. Alternators are rated in....?

KW

KVA

KVAR

HP

incorrect

#2. What is the number of poles if the speed is 3000 rpm and frequency is 50Hz of an alternator?

4

2

6

8

incorrect

N = 120f/P

P= (120 x 50)/3000 = 2

#3. Alternator oerates on the principle of....?

self induction

mutual induction

electromagnetic induction

none of the above

#4. Salient pole alternators used at.....?

low speed applications

high speed applications

high power applications

low power applications

#5. Alternator is also called.....?

synchronous motor

synchronous generator

asynchronous motor

asynchronous generator

#6. A 4 pole 1500 rpm alternator will generate emf at the frequency of......?

40 Hz

50 Hz

60 Hz

20 Hz

N = 120f/p

f = (1500 x 4) /120= 50

#7. The Stator core is laminated, this is to reduce....?

hysteresis loss

eddy current loss

copper loss

frictional loss

#8. In modern alternators, the rotating part is....?

field system

armature

armature as well as field

none of the above

#9. In synchronous machine stator frame is made up of...?

CRGO Steel

silicon steel

cast steel

cast iron or welded steel plates

#10. In synchronous machine stator core is made up of...?

cast iron

silicon steel

cast steel

copper

#11. Which type of alternator used in hydroelectric power station?

salient pole type

non salient pole type

turbo alternator

any of the above

#12. In high speed application which type alternator is used?

salient pole

non salient pole

turbo alternator

none of the above

#13. Which type of alternator used in Steam power station?

turbo alternator

salient pole

non salient pole

any of the above

#14. A 6 pole 60 Hz alternator runs at speed of ..... rpm?

1000

1200

1500

3000

(120 x 60) / 6 =1200

#15. Field system of alternator is excited at use of...?

ac supply

dc supply

ac or dc supply

any of the above

#16. In case of turbo alternators, rotor made of...?

cast iron

cast steel

forged steel

silicon steel

#17. In salient pole structure the pole shoes covers about...?

one half

one third

one fourth

two third

#18. A large diameter and short axial length alternator running at .....?

slow speed

slow and medium speed

high speed

any of the above

#19. Zero power factor method for an alternator is generally used to determine....?

efficiency of alternator

voltage regulation of alternator

synchronous impedence of alternator

any of the above

#20. Damper windings in alternator is to.....?

reduce harmonics

reduce hunting

help in starting

reduce hunting and help in starting

#21. For parallel operation, alternators must have the same?

same voltage ratings

same phase sequence

same frequency

all the above

#22. Most commonly used alternator is......?

revolving armature

revolving field

induction type

none of the above

#23. Cylindrical rotor alternators use ....... ducts for efficient cooling?

only radial

only axial

both radial and axial

none of the above

#24. Skew of rotor bar is to eliminate....?

vibrations

effect of space harmonics

effect of crawling

noise

#25. The stator of modern alternators are wound for ..... phase groups?

60°

180°

120°

240°

#26. The stator poles of an alternator is ......as rotor poles?

less than

greater than

equal to

none of above

#27. Turbo alternators generally used....type rotor?

salient pole

cylindrical pole

any of the above

none of the above

#28. A 3 phase delta connected alternator having a rotating armature will have...?

2 sliprings

3 sliprings

4 sliprings

6 sliprings

#29. The speed of a 6 pole, 60Hz alternator is....?

600 rpm

1200 rpm

1800 rpm

3000 rpm

#30. At no loaded condition, the terminal voltage per phase of alternator is ...... to the generated voltage per phase?

less than

greater than

equal to

any of the above

#31. Calculate the pitch factor for a winding having 36 slots 4 poles with a coil span of 1 to 8?

0.6

0.8

0.94

0.84

#32. The effect of armature reaction in an alternator depends on the....?

resistance of armature

reactance of armature

power factor of the load

impedene

#33. Terminal voltage of an alternator increases with the load when the power factor is.....?

zero

lagging

leading

unity

#34. Alternator said to be over excited when it is operating at.....?

unity power factor

lagging power factor

leading power factor

all the load

#35. The power factor of an alternator is determined by.....?

speed

excitation

current

load

#36. In cylindrical rotor..... portion of rotor is wound?

one third

two third

one half

whole

#37. The angle between induced emf and terminal voltage on no load for a single phase alternator is....?

180°

90°

260°

0°

#38. The effect of leading powerfactor on the voltage regulation of an alternator is.....?

increasing in nature

decreasing in nature

oscillating

constant value

#39. Which method gives more accurate voltage regulation of an alternator?

MMF method

EMF methof

portier triangle method

ZPF method

#40. Which method gives higher than actual value of regulation of an alternator?

ZPF

EMF

ZPF

ASA

#41. In alternator, the leading powerfactor of terminal voltage ...... with load?

decreases

increases

vary

#42. When the load is removed from an AC generator, its terminal voltage rises from 480V at full load to 660 V at noload. calculate the voltage regulation?

25%

35%

37.5%

43.6%

(660-480)/480 = 37.5

#43. The regulation of an alternator is positive when the power factor is....?

zero

lagging

leading

unity

#44. Regulation of an alternator supplying resistive or inductive load is.....?

always positive

always negative

either of the above

none of above

#45. At leading power factor, an alternator.....?

is over excited

is under excited

has no residual magnetism

no effect

#46. What is the cause for hunting effect in alternators?

over load

Due to continuous fluctuation in load

under load

no load

#47. What is the purpose of using damper winding in AC generator?

remove noise

reduce losses

Prevents the hunting effect

increase speed

#48. What is the use of synchroscope?

Adjust the phase sequence

Indicate the correct instant for paralleling

Adjust the voltage

Adjust the frequency

#49. The number of slip rings in a rotating field system type alternator is.....?

2

3

4

1

#50. The rpm of turbo alternator has…?

Low

Medium

High

Any of these

#1. Alternators are rated in....?

#2. What is the number of poles if the speed is 3000 rpm and frequency is 50Hz of an alternator?

#3. Alternator oerates on the principle of....?

#4. Salient pole alternators used at.....?

#5. Alternator is also called.....?

#6. A 4 pole 1500 rpm alternator will generate emf at the frequency of......?

#7. The Stator core is laminated, this is to reduce....?

#8. In modern alternators, the rotating part is....?

#9. In synchronous machine stator frame is made up of...?

#10. In synchronous machine stator core is made up of...?

#11. Which type of alternator used in hydroelectric power station?

#12. In high speed application which type alternator is used?

#13. Which type of alternator used in Steam power station?

#14. A 6 pole 60 Hz alternator runs at speed of ..... rpm?

#15. Field system of alternator is excited at use of...?

#16. In case of turbo alternators, rotor made of...?

#17. In salient pole structure the pole shoes covers about...?

#18. A large diameter and short axial length alternator running at .....?

#19. Zero power factor method for an alternator is generally used to determine....?

#20. Damper windings in alternator is to.....?

#21. For parallel operation, alternators must have the same?

#22. Most commonly used alternator is......?

#23. Cylindrical rotor alternators use ....... ducts for efficient cooling?

#24. Skew of rotor bar is to eliminate....?

#25. The stator of modern alternators are wound for ..... phase groups?

#26. The stator poles of an alternator is ......as rotor poles?

#27. Turbo alternators generally used....type rotor?

#28. A 3 phase delta connected alternator having a rotating armature will have...?

#29. The speed of a 6 pole, 60Hz alternator is....?

#30. At no loaded condition, the terminal voltage per phase of alternator is ...... to the generated voltage per phase?

#31. Calculate the pitch factor for a winding having 36 slots 4 poles with a coil span of 1 to 8?

#32. The effect of armature reaction in an alternator depends on the....?

#33. Terminal voltage of an alternator increases with the load when the power factor is.....?

#34. Alternator said to be over excited when it is operating at.....?

#35. The power factor of an alternator is determined by.....?

#36. In cylindrical rotor..... portion of rotor is wound?

#37. The angle between induced emf and terminal voltage on no load for a single phase alternator is....?

#38. The effect of leading powerfactor on the voltage regulation of an alternator is.....?

#39. Which method gives more accurate voltage regulation of an alternator?

#40. Which method gives higher than actual value of regulation of an alternator?

#41. In alternator, the leading powerfactor of terminal voltage ...... with load?

#42. When the load is removed from an AC generator, its terminal voltage rises from 480V at full load to 660 V at noload. calculate the voltage regulation?

#43. The regulation of an alternator is positive when the power factor is....?

#44. Regulation of an alternator supplying resistive or inductive load is.....?

#45. At leading power factor, an alternator.....?

#46. What is the cause for hunting effect in alternators?

#47. What is the purpose of using damper winding in AC generator?

#48. What is the use of synchroscope?

#49. The number of slip rings in a rotating field system type alternator is.....?

#50. The rpm of turbo alternator has…?

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