Question 1 of 35

1. 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%

Question 1 of 35

Question 2 of 35

2. What condition gives maximum transformer efficiency?

Copper loss > Iron loss

Copper loss = Iron loss

Copper loss < Iron loss

Copper loss = Eddy current loss

Question 2 of 35

Question 3 of 35

3. 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 offer high inductance

To stabilize input/output voltage

Question 3 of 35

Question 4 of 35

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

Windage loss

Eddy current loss

Copper loss

Hysteresis loss

Question 4 of 35

Question 5 of 35

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

Ferrite core transformer

Grain oriented core transformer

Silicon steel core transformer

Ring core transformer

Question 5 of 35

Question 6 of 35

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

Transfers heat to atmosphere

Allows oil expansion due to load variation

Releases internal pressure

Prevents moisture entry

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Question 7 of 35

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

Acidity

Moisture

Dielectric strength

Viscosity

Question 7 of 35

Question 8 of 35

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

Mutually induced EMF

Statically induced EMF

Dynamically induced EMF

Self induced EMF

Question 8 of 35

Question 9 of 35

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

Hysteresis loss only

Core loss

Eddy current loss only

Copper loss

Question 9 of 35

Question 10 of 35

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

Reduces hysteresis loss

Reduces core space

Reduces eddy current loss

Minimizes copper use

Question 10 of 35

Question 11 of 35

11. 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 12 of 35

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

Facilitate 3-phase 4-wire distribution

Avoid overloading

Reduce transformer losses

Maintain constant voltage

Question 12 of 35

Question 13 of 35

13. 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 13 of 35

Question 14 of 35

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

Stepped core arrangement

Laminated core

Grain oriented core

Reduced core thickness

Question 14 of 35

Question 15 of 35

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

Protection from overloading and short circuits

Protection from moisture in oil

Protection from tank pressure

Protection from high temperature

Question 15 of 35

Question 16 of 35

16. How is copper loss determined in transformers?

Impulse test

Short circuit test

Open circuit test

Ratio test

Question 16 of 35

Question 17 of 35

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

Optimize for maximum efficiency

Maintain secondary voltage

Maintain primary voltage

Change distribution voltage ratio

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Question 18 of 35

18. Which transformer measures high voltage installations?

Pulse transformers

Constant voltage transformers

Ignition transformers

Potential transformers

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Question 19 of 35

19. How can potential transformer reading errors be reduced?

Using high flux density material

Using good quality core material

Providing long magnetic path

Using thin laminated core

Question 19 of 35

Question 20 of 35

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

Soft iron

Copper alloy

Rolled steel

Cold rolled grain oriented steel

Question 20 of 35

Question 21 of 35

21. What type of transformer is this?

Air core transformer

Iron core transformer

Ferrite core transformer

Ring core transformer

Question 21 of 35

Question 22 of 35

22. What is this power transformer component called?

Breather

Buchholz relay

Explosion vent

Tap charger

Question 22 of 35

Question 23 of 35

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

Charcoal-salt mixture

Silica gel

Ammonium chloride

Sodium chloride

Question 23 of 35

Question 24 of 35

24. What type of transformer is this?

Auto transformer

Shell type transformer

Core type transformer

Audio frequency transformer

Question 24 of 35

Question 25 of 35

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

Air releasing

Heat releasing

Moisture releasing

Pressure releasing

Question 25 of 35

Question 26 of 35

26. How is moisture controlled in transformer breathers?

Silica gel

Sodium chloride

Ammonium jelly

Transformer oil

Question 26 of 35

Question 27 of 35

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

To minimize the burden

To prevent high static shield

To minimize reading errors

To maintain constant output

Question 27 of 35

Question 28 of 35

28. What is absolutely essential for parallel transformer operation?

Nature of load

Type of cooling

Insulation class

Phase sequence

Question 28 of 35

Question 29 of 35

29. Why are laminated cores used in transformers?

Reduce mechanical loss

Reduce eddy current loss

Reduce copper loss

Reduce hysteresis loss

Question 29 of 35

Question 30 of 35

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

Moisture presence

Overloading condition

High temperature condition

Open circuit condition

Question 30 of 35

Question 31 of 35

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

95% steel, 5% silicon

97% steel, 3% silicon

93% steel, 7% silicon

90% steel, 10% silicon

Question 31 of 35

Question 32 of 35

32. What is the cooling method of transformers?

Oil forced air forced cooling

Oil natural air forced cooling

Oil natural cooling

Oil natural water forced cooling

Question 32 of 35

Question 33 of 35

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

Oil forced air forced

Oil natural air natural

Oil natural air blast

Air natural

Question 33 of 35

Question 34 of 35

34. What is the disadvantage of auto transformers?

Cannot isolate secondary winding

Poor voltage regulation

Heavier weight

More losses

Question 34 of 35

Question 35 of 35

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

Disconnect tappings from neutral

Provide electrical isolation for windings

Disconnect diverter moving contact

Avoid heavy sparking at contacts

Question 35 of 35