Question 1 of 35

1. How is copper loss determined in transformers?

Open circuit test

Impulse test

Short circuit test

Ratio test

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Question 2 of 35

2. Which transformer measures high voltage installations?

Pulse transformers

Potential transformers

Ignition transformers

Constant voltage transformers

Question 2 of 35

Question 3 of 35

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

97% steel, 3% silicon

90% steel, 10% silicon

95% steel, 5% silicon

93% steel, 7% silicon

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Question 4 of 35

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

Reduces eddy current loss

Reduces core space

Reduces hysteresis loss

Minimizes copper use

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Question 5 of 35

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

Releases internal pressure

Prevents moisture entry

Transfers heat to atmosphere

Allows oil expansion due to load variation

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Question 6 of 35

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

Self induced EMF

Statically induced EMF

Mutually induced EMF

Dynamically induced EMF

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Question 7 of 35

7. Why are laminated cores used in transformers?

Reduce hysteresis loss

Reduce mechanical loss

Reduce eddy current loss

Reduce copper loss

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Question 8 of 35

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

Grain oriented core transformer

Ferrite core transformer

Ring core transformer

Silicon steel core transformer

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Question 9 of 35

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

Grain oriented core

Reduced core thickness

Laminated core

Stepped core arrangement

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Question 10 of 35

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

Protection from tank pressure

Protection from moisture in oil

Protection from overloading and short circuits

Protection from high temperature

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Question 11 of 35

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

7.20%

9.09%

8.71%

8.30%

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Question 12 of 35

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

Disconnect diverter moving contact

Avoid heavy sparking at contacts

Disconnect tappings from neutral

Provide electrical isolation for windings

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Question 13 of 35

13. What type of transformer is this?

Ferrite core transformer

Air core transformer

Ring core transformer

Iron core transformer

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Question 14 of 35

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

Eddy current loss only

Hysteresis loss only

Copper loss

Core loss

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Question 15 of 35

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

Copper loss

Hysteresis loss

Windage loss

Eddy current loss

Question 15 of 35

Question 16 of 35

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

Maintain constant voltage

Reduce transformer losses

Facilitate 3-phase 4-wire distribution

Avoid overloading

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Question 17 of 35

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

Ammonium chloride

Sodium chloride

Silica gel

Charcoal-salt mixture

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Question 18 of 35

18. Why are ferrite cores used in radio receivers?

Improve sound quality

Reduce electric interference

Increase receiver efficiency

Reduce constant losses

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Question 19 of 35

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

Open circuit condition

High temperature condition

Moisture presence

Overloading condition

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Question 20 of 35

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

Viscosity

Dielectric strength

Moisture

Acidity

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Question 21 of 35

21. 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 22 of 35

22. How can potential transformer reading errors be reduced?

Using high flux density material

Providing long magnetic path

Using thin laminated core

Using good quality core material

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Question 23 of 35

23. What is absolutely essential for parallel transformer operation?

Phase sequence

Insulation class

Type of cooling

Nature of load

Question 23 of 35

Question 24 of 35

24. What is the disadvantage of auto transformers?

Cannot isolate secondary winding

Heavier weight

More losses

Poor voltage regulation

Question 24 of 35

Question 25 of 35

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

To maintain constant output

To minimize reading errors

To minimize the burden

To prevent high static shield

Question 25 of 35

Question 26 of 35

26. What type of transformer is this?

Shell type transformer

Core type transformer

Auto transformer

Audio frequency transformer

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Question 27 of 35

27. What is this power transformer component called?

Buchholz relay

Breather

Tap charger

Explosion vent

Question 27 of 35

Question 28 of 35

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

Air natural

Oil natural air blast

Oil forced air forced

Oil natural air natural

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Question 29 of 35

29. What condition gives maximum transformer efficiency?

Copper loss = Eddy current loss

Copper loss = Iron loss

Copper loss > Iron loss

Copper loss < Iron loss

Question 29 of 35

Question 30 of 35

30. What is the cooling method of transformers?

Oil natural air forced cooling

Oil forced air forced cooling

Oil natural cooling

Oil natural water forced cooling

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Question 31 of 35

31. How is moisture controlled in transformer breathers?

Silica gel

Sodium chloride

Transformer oil

Ammonium jelly

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Question 32 of 35

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

To offer high inductance

To stabilize input/output voltage

To regulate primary current

To obtain required voltage ratio

Question 32 of 35

Question 33 of 35

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

Pressure releasing

Air releasing

Heat releasing

Moisture releasing

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Question 34 of 35

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

Rolled steel

Soft iron

Cold rolled grain oriented steel

Copper alloy

Question 34 of 35

Question 35 of 35

35. 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 35 of 35