Question 1 of 35

1. 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 1 of 35

Question 2 of 35

2. Why are ferrite cores used in radio receivers?

Reduce constant losses

Increase receiver efficiency

Improve sound quality

Reduce electric interference

Question 2 of 35

Question 3 of 35

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

Pressure releasing

Air releasing

Heat releasing

Moisture releasing

Question 3 of 35

Question 4 of 35

4. What is the disadvantage of auto transformers?

Cannot isolate secondary winding

More losses

Poor voltage regulation

Heavier weight

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Question 5 of 35

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

Disconnect tappings from neutral

Avoid heavy sparking at contacts

Disconnect diverter moving contact

Provide electrical isolation for windings

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Question 6 of 35

6. 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

Question 6 of 35

Question 7 of 35

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

To prevent high static shield

To minimize reading errors

To minimize the burden

To maintain constant output

Question 7 of 35

Question 8 of 35

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

Viscosity

Dielectric strength

Acidity

Moisture

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Question 9 of 35

9. How can potential transformer reading errors be reduced?

Using thin laminated core

Providing long magnetic path

Using good quality core material

Using high flux density material

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Question 10 of 35

10. What type of transformer is this?

Auto transformer

Audio frequency transformer

Shell type transformer

Core type transformer

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Question 11 of 35

11. How is moisture controlled in transformer breathers?

Silica gel

Sodium chloride

Transformer oil

Ammonium jelly

Question 11 of 35

Question 12 of 35

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

Allows oil expansion due to load variation

Prevents moisture entry

Releases internal pressure

Transfers heat to atmosphere

Question 12 of 35

Question 13 of 35

13. Why are laminated cores used in transformers?

Reduce copper loss

Reduce eddy current loss

Reduce hysteresis loss

Reduce mechanical loss

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Question 14 of 35

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

8.71%

8.30%

7.20%

9.09%

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Question 15 of 35

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

93% steel, 7% silicon

90% steel, 10% silicon

95% steel, 5% silicon

97% steel, 3% silicon

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Question 16 of 35

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

Eddy current loss only

Core loss

Copper loss

Hysteresis loss only

Question 16 of 35

Question 17 of 35

17. Which transformer measures high voltage installations?

Constant voltage transformers

Potential transformers

Ignition transformers

Pulse transformers

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Question 18 of 35

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

Maintain constant voltage

Avoid overloading

Facilitate 3-phase 4-wire distribution

Reduce transformer losses

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Question 19 of 35

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

Moisture presence

Open circuit condition

Overloading condition

High temperature condition

Question 19 of 35

Question 20 of 35

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

Grain oriented core transformer

Ring core transformer

Ferrite core transformer

Silicon steel core transformer

Question 20 of 35

Question 21 of 35

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

Air natural

Oil natural air blast

Oil natural air natural

Oil forced air forced

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 stabilize input/output voltage

To offer high inductance

To regulate primary current

Question 22 of 35

Question 23 of 35

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

Soft iron

Rolled steel

Copper alloy

Cold rolled grain oriented steel

Question 23 of 35

Question 24 of 35

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

Optimize for maximum efficiency

Change distribution voltage ratio

Maintain primary voltage

Maintain secondary voltage

Question 24 of 35

Question 25 of 35

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

Self induced EMF

Statically induced EMF

Mutually induced EMF

Dynamically induced EMF

Question 25 of 35

Question 26 of 35

26. What type of transformer is this?

Air core transformer

Ring core transformer

Iron core transformer

Ferrite core transformer

Question 26 of 35

Question 27 of 35

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

Sodium chloride

Silica gel

Charcoal-salt mixture

Ammonium chloride

Question 27 of 35

Question 28 of 35

28. What is this power transformer component called?

Buchholz relay

Tap charger

Explosion vent

Breather

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Question 29 of 35

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

Reduces eddy current loss

Reduces hysteresis loss

Minimizes copper use

Reduces core space

Question 29 of 35

Question 30 of 35

30. What condition gives maximum transformer efficiency?

Copper loss = Iron loss

Copper loss < Iron loss

Copper loss = Eddy current loss

Copper loss > Iron loss

Question 30 of 35

Question 31 of 35

31. How is copper loss determined in transformers?

Ratio test

Open circuit test

Impulse test

Short circuit test

Question 31 of 35

Question 32 of 35

32. What is the cooling method of transformers?

Oil forced air forced cooling

Oil natural water forced cooling

Oil natural air forced cooling

Oil natural cooling

Question 32 of 35

Question 33 of 35

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

Copper loss

Eddy current loss

Windage loss

Hysteresis loss

Question 33 of 35

Question 34 of 35

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

Laminated core

Stepped core arrangement

Reduced core thickness

Grain oriented core

Question 34 of 35

Question 35 of 35

35. What is absolutely essential for parallel transformer operation?

Phase sequence

Insulation class

Nature of load

Type of cooling

Question 35 of 35