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Transformer Interview Questions and Answers pdf

Transformer: [ ISRO,DRDO,DMRC,SAIL, ODNANCE, HAL, WBSEDCL, RAILWAY
& Others competitive]

21. The chemical used in breather for transformer should have the quality of……(ISRO, ORDNANCE , DMRC , DRDO Repeated )

1.ionizing air

2.absorbing moisture

3.cleansing the transformer oil

4.cooling the transformer oil

22. The chemical used in breather is…... (ISRO, ORDNANCE , DMRC , DRDO Repeated )

1.asbestos fiber

2.silica sand

3.sodium chloride

4.   silica gel

23.A good transformer oil should be free from ….

1.Sulphur

2.alkali

3. moisture

4.   all the above

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24. An ideal transformer has infinite values of primary and secondary inductances. The statement is

1.true

2.  false

25. An ideal transformer ratings are usually expressed in terms of

1.volts

2.amperes

3.kW

4.  kVA

26. The noise resulting from vibrations of laminations set by magnetic force, is termed as

1.magnetostriction

2. boo

3.   hum

4. zoom

27. Hysteresis loss in a transformer varies as (Bmax= maximum flux density)

1.Bmax

2.  Bmax1.6

3.Bmax2

4.Bmax2.4

28. Material used for construction of transformer core is usually

1.wood

2.copper

3.aluminum

4.  silicon steel

 

29. The thickness of laminations used in a transformer is usually… (ISRO, ORDNANCE , DMRC , DRDO Repeated )

1.  0.4 mm to 0.5 mm

2.4 mm to 5 mm

3.14 mm to 15 mm

4.25 mm to 40 mm

30. The function of conservator in a transformer is

 

1.to protect against internal fault

2.to reduce copper as well as core losses

3.to cool the transformer oil

4.to take case of the expansion and contraction of transformer oil due to variation of temperature of surroundings

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Transformer Interview Questions and Answers pdf

Transformer: [ ISRO,DRDO,DMRC,SAIL, ODNANCE, HAL, WBSEDCL, RAILWAY
& Others competitive]

11.Sumpner’s test is conducted on transformers to determine

1.temperature

2.stray losses

3.all-day efficiency

4.none of the above

12. The permissible flux density in case of cold rolled grain oriental steel is around

1.1.7 Wb/m2

2.   2.7 Wb/m2

3.  3.7 Wb/m2

4.  4.7 Wb/m2

13. During the short-circuit test on a small transformer the frequency is increased from 50 Hz to 200 Hz. The copper losses will increase by a factor of…

1.  16

2.4

3.4

4.¼ .

14. The efficiency of a transformer will be maximum when……..(ISRO, ORDNANCE , DMRC , DRDO Repeated )

1.copper losses = hysteresis losses

2.hysteresis losses = eddy current losses

3.eddy current losses = copper losses

4.copper losses = iron losses

15. No-load current in a transformer is … (ISRO, ORDNANCE , DMRC , DRDO Repeated )

1.  lags behind the voltage by about 750

2.leads the voltage by about 750

3.lags behind the voltage by about 150

4.leads the voltage by about 150

16. The purpose of providing the iron core in a transformer is to

1.provide support to windings

2.reduce hysteresis loss

3.decrease the reluctance of the magnetic path

4.reduce eddy current losses.

17. Which of the following is not a part of transformer installation? ( ORDNANCE Repeated )

1.Conservator

2.Breather

3.Buchholz relay

4.  Exciter

18. Which conducting short-circuit test on a transformer the following side is short-circuited…..(ISRO, ORDNANCE , DMRC , DRDO Repeated )

1.high voltage side

2.low voltage side

3.primary side

4.secondary side

19. In a transformer the toppings are generally provided on…… ( ORDNANCE  Repeated )

1.primary side

2.secondary side

3.low voltage side

4.high voltage side

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 20. The use of higher flux density in the transformer design…..(ISRO, ORDNANCE , DMRC , DRDO Repeated )                   

1.  reduces weight per kVA

2.reduces iron losses

3.reduces copper losses

4.increases part load efficiency

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ISRO Previous Years Question paper pdf technician- B (electrician)

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Top 100 MCQ Transformer questions and answers

 

Transformer: [ ISRO,DRDO,DMRC,SAIL, ODNANCE, HAL, WBSEDCL, RAILWAY
& Others competitive]

91. The efficiency of a transformer, under heavy loads, is comparatively low because

(a) copper loss becomes high in proportion to the output

(b) iron loss is increased considerably

(c) voltage drop both in primary and secondary becomes large

(d) secondary output is much less as compared to primary input

Ans: a

92. An open-circuit test on a transformer is conducted primarily to measure

(a) insulation resistance

(b) copper loss

(c) core loss

(d) total loss

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Ans: c

93. A no-load test is performed on a transformer to determine

(a) core loss

 (b) efficiency

(c) magnetising current

(d) magnetising current and loss

Ans: d

94. The voltage transformation ratio of a transformer is equal to the ratio of

(a) primary turns to secondary turns

(b) secondary current to primary current

(c) secondary induced e.m.f. to primary induced e.m.f.

(d) secondary terminal voltage to primary applied voltage

Ans: c

95. Part of the transformer which is most subject to damage from overheating is

(a) iron core

(b) copper winding

(c) winding insulation

(d) frame or case

Ans: c

96.For a transformer, operating at constant load current, maximum efficiency will occur at …

(a) 0.8 leading power factor

(b) 0.8 lagging power factor

(c) zero power factor

(d) unity power factor

Ans: d

97. Which of the following protection is normally not provided on small distribution transformers?

(a) Over fluxing protection

(b) Buchholz relay

(c) Overcurrent protection

(d) All of the above

Ans: b

98.Which of the following acts as a protection against high voltage surges due to lightning and switching?

(a) Horn gaps

(b) Thermal overload relays

(c) Breather

(d) Conservator

Ans: a

99.The efficiency of two identical transformers under load conditions can be determined by

(a) short-circuit test

(b) back-to-back test

(c) open circuit test

(d) any of the above

Ans: b

100.Which of the following insulating materials can withstand the highest temperature safely?

(a) Cellulose

(b) Asbestos

(c) Mica

(d) Glass fibre

Ans: c

 

 All the best for competitive Exam.

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ISRO Previous Years Question paper pdf technician- B (electrician)

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Transformer MCQ pdf practice

Transformer: [ ISRO,DRDO,DMRC,SAIL, ODNANCE, HAL, WBSEDCL, RAILWAY
& Others competitive]

81. Auto-transformer makes effective saving on copper and copper losses, when its transformation ratio is
(a) approximately equal to one
(b) less than one
(c) great than one
(d) none of the above
Ans: a
82. Minimum voltage regulation occurs when the power factor of the load is
(a) unity
(b) lagging
(c) leading
(d) zero
Ans: c

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83. In a step-down transformer, there is a change of 15 A in the load
current. This results in change of supply current of

(a) less than 15 A
(b) more than 15 A
(c) 15 A
(d) none of the above
Ans: a
84. The efficiencies of transformers compared with that of electric motors of the same power are
(a) about the same
(b) much smaller
(c) much higher
(d) somewhat smaller
Ans: c

85. The noise produced by a transformer is termed as

(a) zoom

(b) hum

(c) ringing

(d) buzz

Ans: b

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86. Which of the following loss in a transformer is zero even at full load ?

(a) Core loss

(b) Friction loss

(c) Eddy current loss

(d) Hysteresis loss

Ans: b

87. Which of the following is the most likely source of harmonics in a transformer ?

(a) poor insulation

(b) Overload

(c) loose connections

(d) Core saturation

Ans: d

88. If a transformer is continuously operated the maximum temperature rise will occur in…

(a) core

(b) windings

(c) tank

(d) any of the above

Ans: b

89. The hum in a transformer is mainly attributed to

(a) load changes

(b) oil in the transformer

(c) magnetostriction

d. mechanical vibrations 

Ans: c

90. The maximum load that a power transformer can carry is limited by its

(a) temperature rise

(b) dielectric strength of oil

(c) voltage ratio

(d) copper loss

Ans: c

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ISRO Previous Years Question paper pdf technician- B (electrician)

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Previous Years Question Paper
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