Question 1 of 35

1. What type of transformer is this?

Core type transformer

Audio frequency transformer

Auto transformer

Shell type transformer

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Question 2 of 35

2. What is the purpose of tap changing in power transformers?

Optimize for maximum efficiency

Maintain primary voltage

Maintain secondary voltage

Change distribution voltage ratio

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Question 3 of 35

3. What is the function of Buchholz relay in power transformers?

Protection from tank pressure

Protection from high temperature

Protection from overloading and short circuits

Protection from moisture in oil

Question 3 of 35

Question 4 of 35

4. Which transformer loss is determined by short circuit test?

Copper loss

Hysteresis loss

Windage loss

Eddy current loss

Question 4 of 35

Question 5 of 35

5. What does the crackle test of transformer oil determine?

Dielectric strength

Acidity

Moisture

Viscosity

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Question 6 of 35

6. What type of EMF is induced in an ideal two-winding transformer?

Dynamically induced EMF

Mutually induced EMF

Statically induced EMF

Self induced EMF

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Question 7 of 35

7. What is absolutely essential for parallel transformer operation?

Insulation class

Nature of load

Phase sequence

Type of cooling

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Question 8 of 35

8. How can potential transformer reading errors be reduced?

Using good quality core material

Providing long magnetic path

Using thin laminated core

Using high flux density material

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Question 9 of 35

9. Why are ferrite cores used in radio receivers?

Increase receiver efficiency

Improve sound quality

Reduce constant losses

Reduce electric interference

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Question 10 of 35

10. Why is load disconnected before OFF-load tap changing?

Disconnect diverter moving contact

Provide electrical isolation for windings

Disconnect tappings from neutral

Avoid heavy sparking at contacts

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Question 11 of 35

11. Which type of transformer is used for high frequency applications?

Ring core transformer

Grain oriented core transformer

Ferrite core transformer

Silicon steel core transformer

Question 11 of 35

Question 12 of 35

12. What type of transformer is this?

Ring core transformer

Iron core transformer

Air core transformer

Ferrite core transformer

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Question 13 of 35

13. What is the composition of silicon steel in transformer cores?

97% steel, 3% silicon

93% steel, 7% silicon

95% steel, 5% silicon

90% steel, 10% silicon

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Question 14 of 35

14. Why are laminated cores used in transformers?

Reduce hysteresis loss

Reduce mechanical loss

Reduce copper loss

Reduce eddy current loss

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Question 15 of 35

15. Which material is used to make the core of power transformers?

Rolled steel

Cold rolled grain oriented steel

Soft iron

Copper alloy

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Question 16 of 35

16. What is the relationship between primary voltage (E₁ V₁ ) and secondary voltage (E₂, V₂) in an ideal transformer?

E₁ = V₁ and E₂ = V₂

E₁ > V₁ and E₂ > V₂

E₁ < V₁ and E₂ < V₂

E₁= V₁ and E₂ = V₂

Question 16 of 35

Question 17 of 35

17. What is the function of a conservator in a transformer?

Prevents moisture entry

Allows oil expansion due to load variation

Transfers heat to atmosphere

Releases internal pressure

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Question 18 of 35

18. How is copper loss determined in transformers?

Short circuit test

Ratio test

Impulse test

Open circuit test

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Question 19 of 35

19. Why is the primary of a potential transformer wound with thin wire and many turns?

To obtain required voltage ratio

To regulate primary current

To stabilize input/output voltage

To offer high inductance

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Question 20 of 35

20. What is the purpose of an explosion vent in power transformers?

Air releasing

Pressure releasing

Moisture releasing

Heat releasing

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Question 21 of 35

21. What is the cooling method of transformers?

Oil natural water forced cooling

Oil forced air forced cooling

Oil natural air forced cooling

Oil natural cooling

Question 21 of 35

Question 22 of 35

22. Which transformer measures high voltage installations?

Potential transformers

Pulse transformers

Ignition transformers

Constant voltage transformers

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Question 23 of 35

23. What material is used in breathers to prevent moisture in transformer oil?

Ammonium chloride

Silica gel

Sodium chloride

Charcoal-salt mixture

Question 23 of 35

Question 24 of 35

24. Why does a current transformer core have low reactance and low core losses?

To minimize the burden

To prevent high static shield

To maintain constant output

To minimize reading errors

Question 24 of 35

Question 25 of 35

25. What condition gives maximum transformer efficiency?

Copper loss = Iron loss

Copper loss < Iron loss

Copper loss = Eddy current loss

Copper loss > Iron loss

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Question 26 of 35

26. Which cooling method is used in pole-mounted distribution transformers?

Oil natural air blast

Oil natural air natural

Air natural

Oil forced air forced

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Question 27 of 35

27. What is the disadvantage of auto transformers?

Cannot isolate secondary winding

More losses

Heavier weight

Poor voltage regulation

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Question 28 of 35

28. What activates the top float switch in a Buchholz relay?

Moisture presence

Open circuit condition

Overloading condition

High temperature condition

Question 28 of 35

Question 29 of 35

29. Which loss is assessed by open-circuit test?

Eddy current loss only

Hysteresis loss only

Core loss

Copper loss

Question 29 of 35

Question 30 of 35

30. Why are distribution transformers typically delta-primary and star-secondary?

Facilitate 3-phase 4-wire distribution

Reduce transformer losses

Avoid overloading

Maintain constant voltage

Question 30 of 35

Question 31 of 35

31. Which construction technique reduces copper loss in large transformers?

Stepped core arrangement

Laminated core

Grain oriented core

Reduced core thickness

Question 31 of 35

Question 32 of 35

32. What is this power transformer component called?

Breather

Explosion vent

Tap charger

Buchholz relay

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Question 33 of 35

33. What is the advantage of stepped core in large transformers?

Reduces core space

Reduces eddy current loss

Reduces hysteresis loss

Minimizes copper use

Question 33 of 35

Question 34 of 35

34. How is moisture controlled in transformer breathers?

Sodium chloride

Transformer oil

Ammonium jelly

Silica gel

Question 34 of 35

Question 35 of 35

35. Calculate the voltage regulation percentage if no-load voltage is 240V and full-load voltage is 220V:

9.09%

8.71%

8.30%

7.20%

Question 35 of 35