Question 1 of 35

1. What type of transformer is this?

Ferrite core transformer

Iron core transformer

Ring core transformer

Air core transformer

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Question 2 of 35

2. What is absolutely essential for parallel transformer operation?

Type of cooling

Nature of load

Phase sequence

Insulation class

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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 moisture in oil

Protection from overloading and short circuits

Question 3 of 35

Question 4 of 35

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

Self induced EMF

Mutually induced EMF

Dynamically induced EMF

Statically induced EMF

Question 4 of 35

Question 5 of 35

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

Overloading condition

Open circuit condition

Moisture presence

High temperature condition

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Question 6 of 35

6. What condition gives maximum transformer efficiency?

Copper loss < Iron loss

Copper loss > Iron loss

Copper loss = Iron loss

Copper loss = Eddy current loss

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Question 7 of 35

7. What is this power transformer component called?

Breather

Buchholz relay

Tap charger

Explosion vent

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Question 8 of 35

8. How is moisture controlled in transformer breathers?

Ammonium jelly

Transformer oil

Sodium chloride

Silica gel

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Question 9 of 35

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

7.20%

8.71%

8.30%

9.09%

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Question 10 of 35

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

Oil forced air forced

Air natural

Oil natural air natural

Oil natural air blast

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Question 11 of 35

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

To minimize reading errors

To prevent high static shield

To maintain constant output

To minimize the burden

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Question 12 of 35

12. Why are laminated cores used in transformers?

Reduce mechanical loss

Reduce eddy current loss

Reduce hysteresis loss

Reduce copper loss

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Question 13 of 35

13. Why are ferrite cores used in radio receivers?

Reduce electric interference

Improve sound quality

Reduce constant losses

Increase receiver efficiency

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Question 14 of 35

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

Avoid overloading

Maintain constant voltage

Reduce transformer losses

Facilitate 3-phase 4-wire distribution

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Question 15 of 35

15. What type of transformer is this?

Core type transformer

Shell type transformer

Audio frequency transformer

Auto transformer

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Question 16 of 35

16. What is the disadvantage of auto transformers?

Poor voltage regulation

More losses

Cannot isolate secondary winding

Heavier weight

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Question 17 of 35

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

Soft iron

Copper alloy

Cold rolled grain oriented steel

Rolled steel

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Question 18 of 35

18. Which transformer measures high voltage installations?

Ignition transformers

Pulse transformers

Potential transformers

Constant voltage transformers

Question 18 of 35

Question 19 of 35

19. 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 20 of 35

20. 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 20 of 35

Question 21 of 35

21. How is copper loss determined in transformers?

Ratio test

Open circuit test

Short circuit test

Impulse test

Question 21 of 35

Question 22 of 35

22. 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

Question 22 of 35

Question 23 of 35

23. What is the cooling method of transformers?

Oil natural cooling

Oil natural water forced cooling

Oil forced air forced cooling

Oil natural air forced cooling

Question 23 of 35

Question 24 of 35

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

Disconnect diverter moving contact

Provide electrical isolation for windings

Avoid heavy sparking at contacts

Disconnect tappings from neutral

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Question 25 of 35

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

Air releasing

Moisture releasing

Heat releasing

Pressure releasing

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Question 26 of 35

26. How can potential transformer reading errors be reduced?

Using thin laminated core

Providing long magnetic path

Using high flux density material

Using good quality core material

Question 26 of 35

Question 27 of 35

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

Core loss

Hysteresis loss only

Eddy current loss only

Copper loss

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Question 28 of 35

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

Reduces hysteresis loss

Minimizes copper use

Reduces core space

Reduces eddy current loss

Question 28 of 35

Question 29 of 35

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

Maintain primary voltage

Optimize for maximum efficiency

Change distribution voltage ratio

Maintain secondary voltage

Question 29 of 35

Question 30 of 35

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

Grain oriented core

Stepped core arrangement

Reduced core thickness

Laminated core

Question 30 of 35

Question 31 of 35

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

90% steel, 10% silicon

95% steel, 5% silicon

93% steel, 7% silicon

97% steel, 3% silicon

Question 31 of 35

Question 32 of 35

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

Moisture

Dielectric strength

Acidity

Viscosity

Question 32 of 35

Question 33 of 35

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

Silica gel

Ammonium chloride

Charcoal-salt mixture

Sodium chloride

Question 33 of 35

Question 34 of 35

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

Hysteresis loss

Windage loss

Copper loss

Eddy current loss

Question 34 of 35

Question 35 of 35

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

Ferrite core transformer

Ring core transformer

Silicon steel core transformer

Grain oriented core transformer

Question 35 of 35