Transformers

#1. Transformers are working on the principle of…..?

self induction

mutual induction

faraday's law

eddy current

#2. The rating of transformer expressed in…..?

kVA

kW

kVAR

volt

#3. A transformer varies the output…..?

frequency

power

voltage

energy

#4. The efficiency of the transformer is generally…..?

25%

50%

75%

97%

#5. Transformers operates…..?

at unity power factor

at lagging power factor

at a power factor depending on the load power factor

at leading power factor

#6. Which material is most suitable for making transformer core is…..?

Silicon steel

Iron

CRGO silicon steel

HRGO silicon steel

reduce hysteresis loss

#7. Stepped core arrangement in larger transformer reduce….?

minimise the use of copper

reduce copper loss

all the above

#8. Area of hysteresis loop represents….?

copper loss

eddy current loss

hysteresis loss

dielectric loss

#9. The transformer used for AC welding is…..?

step up

step down

booster type

autotransformer

#10. A transformer has maximum efficiency at full load, when iron losses are 800 watts copper losses at half load will be….?

200W

400W

800W

1600W

I= Ifl/2

half load = 800/4=200w

#11. The purpose of conservator in transformer is….?

to cooling

to insulation

prevent entering moisture

to take up contraction and expansion of oil

#12. Power transformer are designed for maximum efficiency occurs at…..?

half load

one fourth of load

near full load

all load

#13. Transformer core is laminated to avoid loss of energy due to….?

heating

copper loss

eddy current

hysteresis

#14. Which material used for making transformer core?

Alnico

steel

soft iron

copper

#15. Buchholz relay is used for…?

auto transformer

current transformer

power transformer

potential transformer

#16. Buchholz relay is used for…?

zero power factor load

leading power factor load

lagging power factor load

all the above

#17. A transformer has negative voltage regulation when its load power factor is….?

zero

unity

leading

lagging

#18. A transformer has negative voltage regulation when its load power factor is….?

zero

5 ohms

15 ohms

50 ohms

#19. The purpose of oil in a transformer is to…..?

lubricate

cooling

insulation

insulate and cool

#20. Short circuit test of transformer gives…..losses?

copper

iron

eddy current

hydteresis

#21. Short circuit test of transformer gives…..losses?

copper

iron

eddy current

hydteresis

#22. The standard value of secondary current of current transformer is….?

3A

5A

10A

20A

#23. The standard value of secondary current of current transformer is….?

1

100

20

0.1

#24. Ordinary transformer doesnot change its…..?

back to back test

open circuit test

short circuit test

all the above

#25. Ordinary transformer doesnot change its…..?

voltage

frequency

current

all the above

#26. The two windings of transformer are…..?

electrically linked

conductively linkef

inductively linked

all the above

#27. The iron core of transformer provide ….. path to the main flux?

low resistance

high resistance

low reluctance

high reluctance

#28. An ideal transformer doesnot change its…..?

voltage

current

power

frequency

#29. The condition of maximum efficiency of the transformer is that…..?

copper loss = iron loss

copper loss<iron loss

copper loss>iron loss

copper loss =0

#30. The core loss in a transformer is constant during….?

half load

full load

all load

quarter load

#31. Which type of winding used in shell type transformer?

circular

rectangular

sandwitch

all the above

#32. In a transformer conservator placed on….?

inside tank

top of the tank

bottom of the tank

outside of tank

#33. A transformer has full load copper loss is 800 W. at half load copper loss is…..?

250W

400W

200 W

100W

#34. During open circuit test of a transformer primary is supplied at….?

rated current

rated voltage

reduced voltage

reduced current

#35. If dc voltage is applied to the primary of a transformer it may?

work

not work

burn the primary winding

lower the output voltage

#36. A distribution transformer usually is a….?

star delta transformer

delta star transformer

star star transformer

delta delta transformer

#37. In an ideal transformer, the no load primary current ……?

is in phase with voltage

lags behind voltage by 90

leads voltage by 90

none of the above

#38. In any single phase transformer the primary and secondary induced voltages are……?

90° out of phase

180° out of phase

in phase

#39. No load current of a transformer interms of the full load current is usually…..?

5 to 10%

1 to 3%

10 to 50%

5 to 20%

#40. The all day efficiency of a transformer is the ratio of the……?

output power and input power

input power and output power

KWH output and KWH input in a day

none of the above

#41. Distribution transformers designed for maximum efficiency at …..%?

25

60

70

100

#42. Natural air cooling transformers of rating upto…..?

100 kVA

5 -10 kVA

200 kVA

500 kVA

#43. A buchholz relay is used for protection against…..?

all internal faults

all external faults

both internal and external faultd

#44. Scott connection are used for…..?

single phase to three phase transformation

three phase to single phase transformation

three phase to two phase transformation

any of the above

#45. In scott connection, teaser transformer operates on 0.866 of its rated….?

current

voltage

power

resistance

#46. Constant current transformer is of…..type?

core

shell

core or shell

none of the above

#47. The size of transformer core depends upon….?

frequency

flux density in the core material

area of core

frequency and flux density of core

#48. Which is the common method of cooling a power transformer?

air cooling

oil cooling

oil cooling with air blast

air blast cooling

#49. In scott connection the neutral point divides the teaser winding in the ratio of…..?

1:1

1:2

1:3

1:4

#50. In a three phase delta transformer, one of the phase burnt. the transformer will supply…..?

its full output voltage

zero output

75% output rating

58% of its output rating

#51. The main purpose of core in a transformer is to…..?

carry primary current

prevent eddy current

eliminate hysteresis loss

decrease reluctance of magnetic circuit

#52. Buchholz relay is …… type relay?

solenoid

thermal

induction

attracted armature type

#53. Turns ratio of isolation or one to one transformer is…..?

zero

one

less than one

greater than one

#54. The type of transformer used in battery charger is…?

step up transformer

step down transformer

current transformer

potential transformer

#55. The essential condition for the parallel operation of two single phase transformers should be…..?

same voltage

same per unit impedence

same phase sequence

all the above

#56. The condition for maximum efficiency in a transformer is…..?

total loss is zero

copper loss is zero

copper loss = iron loss

iron loss is zro

#57. The impedance ratio of transformer is equal to….?

transformer ratio

inverse of transformer ratio

square of transformr ratio

inverse of square of transformer ratio

#58. Scott connection of transformer is also known as….?

X-X

T-T

Y-Y

V-V

#59. A transformer has negative voltage regulation when its load power factor is….?

Leading

unity

lagging

zero

#60. A T-T transformer cannot be paralleled with ….transformer?

Y-Δ

V-V

Y-Y

Δ-Δ

#1. Transformers are working on the principle of…..?

#2. The rating of transformer expressed in…..?

#3. A transformer varies the output…..?

#4. The efficiency of the transformer is generally…..?

#5. Transformers operates…..?

#6. Which material is most suitable for making transformer core is…..?

#7. Stepped core arrangement in larger transformer reduce….?

#8. Area of hysteresis loop represents….?

#9. The transformer used for AC welding is…..?

#10. A transformer has maximum efficiency at full load, when iron losses are 800 watts copper losses at half load will be….?

#11. The purpose of conservator in transformer is….?

#12. Power transformer are designed for maximum efficiency occurs at…..?

#13. Transformer core is laminated to avoid loss of energy due to….?

#14. Which material used for making transformer core?

#15. Buchholz relay is used for…?

#16. Buchholz relay is used for…?

#17. A transformer has negative voltage regulation when its load power factor is….?

#18. A transformer has negative voltage regulation when its load power factor is….?

#19. The purpose of oil in a transformer is to…..?

#20. Short circuit test of transformer gives…..losses?

#21. Short circuit test of transformer gives…..losses?

#22. The standard value of secondary current of current transformer is….?

#23. The standard value of secondary current of current transformer is….?

#24. Ordinary transformer doesnot change its…..?

#25. Ordinary transformer doesnot change its…..?

#26. The two windings of transformer are…..?

#27. The iron core of transformer provide ….. path to the main flux?

#28. An ideal transformer doesnot change its…..?

#29. The condition of maximum efficiency of the transformer is that…..?

#30. The core loss in a transformer is constant during….?

#31. Which type of winding used in shell type transformer?

#32. In a transformer conservator placed on….?

#33. A transformer has full load copper loss is 800 W. at half load copper loss is…..?

#34. During open circuit test of a transformer primary is supplied at….?

#35. If dc voltage is applied to the primary of a transformer it may?

#36. A distribution transformer usually is a….?

#37. In an ideal transformer, the no load primary current ……?

#38. In any single phase transformer the primary and secondary induced voltages are……?

#39. No load current of a transformer interms of the full load current is usually…..?

#40. The all day efficiency of a transformer is the ratio of the……?

#41. Distribution transformers designed for maximum efficiency at …..%?

#42. Natural air cooling transformers of rating upto…..?

#43. A buchholz relay is used for protection against…..?

#44. Scott connection are used for…..?

#45. In scott connection, teaser transformer operates on 0.866 of its rated….?

#46. Constant current transformer is of…..type?

#47. The size of transformer core depends upon….?

#48. Which is the common method of cooling a power transformer?

#49. In scott connection the neutral point divides the teaser winding in the ratio of…..?

#50. In a three phase delta transformer, one of the phase burnt. the transformer will supply…..?

#51. The main purpose of core in a transformer is to…..?

#52. Buchholz relay is …… type relay?

#53. Turns ratio of isolation or one to one transformer is…..?

#54. The type of transformer used in battery charger is…?

#55. The essential condition for the parallel operation of two single phase transformers should be…..?

#56. The condition for maximum efficiency in a transformer is…..?

#57. The impedance ratio of transformer is equal to….?

#58. Scott connection of transformer is also known as….?

#59. A transformer has negative voltage regulation when its load power factor is….?

#60. A T-T transformer cannot be paralleled with ….transformer?

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