Question 1 of 35

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

Copper alloy

Rolled steel

Cold rolled grain oriented steel

Soft iron

Question 1 of 35

Question 2 of 35

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

Sodium chloride

Ammonium chloride

Charcoal-salt mixture

Silica gel

Question 2 of 35

Question 3 of 35

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

Acidity

Moisture

Viscosity

Dielectric strength

Question 3 of 35

Question 4 of 35

4. What type of transformer is this?

Air core transformer

Iron core transformer

Ring core transformer

Ferrite core transformer

Question 4 of 35

Question 5 of 35

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

Core loss

Hysteresis loss only

Copper loss

Eddy current loss only

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Question 6 of 35

6. How is copper loss determined in transformers?

Impulse test

Open circuit test

Short circuit test

Ratio test

Question 6 of 35

Question 7 of 35

7. 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 7 of 35

Question 8 of 35

8. What is the disadvantage of auto transformers?

Cannot isolate secondary winding

More losses

Heavier weight

Poor voltage regulation

Question 8 of 35

Question 9 of 35

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

Maintain secondary voltage

Maintain primary voltage

Optimize for maximum efficiency

Change distribution voltage ratio

Question 9 of 35

Question 10 of 35

10. Which transformer measures high voltage installations?

Constant voltage transformers

Ignition transformers

Potential transformers

Pulse transformers

Question 10 of 35

Question 11 of 35

11. What is absolutely essential for parallel transformer operation?

Phase sequence

Nature of load

Type of cooling

Insulation class

Question 11 of 35

Question 12 of 35

12. How is moisture controlled in transformer breathers?

Silica gel

Transformer oil

Sodium chloride

Ammonium jelly

Question 12 of 35

Question 13 of 35

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

Copper loss

Hysteresis loss

Eddy current loss

Windage loss

Question 13 of 35

Question 14 of 35

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

Facilitate 3-phase 4-wire distribution

Reduce transformer losses

Maintain constant voltage

Avoid overloading

Question 14 of 35

Question 15 of 35

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

To stabilize input/output voltage

To regulate primary current

To offer high inductance

To obtain required voltage ratio

Question 15 of 35

Question 16 of 35

16. What condition gives maximum transformer efficiency?

Copper loss > Iron loss

Copper loss = Eddy current loss

Copper loss < Iron loss

Copper loss = Iron loss

Question 16 of 35

Question 17 of 35

17. What is the cooling method of transformers?

Oil natural air forced cooling

Oil natural cooling

Oil natural water forced cooling

Oil forced air forced cooling

Question 17 of 35

Question 18 of 35

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

Laminated core

Stepped core arrangement

Reduced core thickness

Grain oriented core

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Question 19 of 35

19. Why are ferrite cores used in radio receivers?

Reduce constant losses

Increase receiver efficiency

Improve sound quality

Reduce electric interference

Question 19 of 35

Question 20 of 35

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

Air natural

Oil natural air natural

Oil natural air blast

Oil forced air forced

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Question 21 of 35

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

Protection from overloading and short circuits

Protection from high temperature

Protection from moisture in oil

Protection from tank pressure

Question 21 of 35

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

Question 22 of 35

Question 23 of 35

23. What is this power transformer component called?

Buchholz relay

Explosion vent

Breather

Tap charger

Question 23 of 35

Question 24 of 35

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

Prevents moisture entry

Releases internal pressure

Transfers heat to atmosphere

Allows oil expansion due to load variation

Question 24 of 35

Question 25 of 35

25. 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

Question 25 of 35

Question 26 of 35

26. Why are laminated cores used in transformers?

Reduce mechanical loss

Reduce hysteresis loss

Reduce copper loss

Reduce eddy current loss

Question 26 of 35

Question 27 of 35

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

9.09%

8.71%

7.20%

8.30%

Question 27 of 35

Question 28 of 35

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

95% steel, 5% silicon

97% steel, 3% silicon

90% steel, 10% silicon

93% steel, 7% silicon

Question 28 of 35

Question 29 of 35

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

To prevent high static shield

To maintain constant output

To minimize the burden

To minimize reading errors

Question 29 of 35

Question 30 of 35

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

Overloading condition

Moisture presence

High temperature condition

Open circuit condition

Question 30 of 35

Question 31 of 35

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

Grain oriented core transformer

Silicon steel core transformer

Ferrite core transformer

Ring core transformer

Question 31 of 35

Question 32 of 35

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

Dynamically induced EMF

Statically induced EMF

Mutually induced EMF

Self induced EMF

Question 32 of 35

Question 33 of 35

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

Air releasing

Moisture releasing

Pressure releasing

Heat releasing

Question 33 of 35

Question 34 of 35

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

Reduces hysteresis loss

Reduces core space

Reduces eddy current loss

Minimizes copper use

Question 34 of 35

Question 35 of 35

35. What type of transformer is this?

Core type transformer

Shell type transformer

Auto transformer

Audio frequency transformer

Question 35 of 35