ELECTRICIAN 1st YEAR MODULE -Transformer

Question 1 of 35

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

Ferrite core transformer

Ring core transformer

Silicon steel core transformer

Grain oriented core transformer

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Question 2 of 35

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

Pressure releasing

Moisture releasing

Heat releasing

Air releasing

Question 2 of 35

Question 3 of 35

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

Eddy current loss only

Copper loss

Core loss

Hysteresis loss only

Question 3 of 35

Question 4 of 35

4. What type of transformer is this?

Ring core transformer

Air core transformer

Ferrite core transformer

Iron core transformer

Question 4 of 35

Question 5 of 35

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

Prevents moisture entry

Transfers heat to atmosphere

Allows oil expansion due to load variation

Releases internal pressure

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Question 6 of 35

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

Disconnect tappings from neutral

Disconnect diverter moving contact

Avoid heavy sparking at contacts

Provide electrical isolation for windings

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Question 7 of 35

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

Protection from overloading and short circuits

Protection from tank pressure

Protection from high temperature

Protection from moisture in oil

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Question 8 of 35

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

Rolled steel

Soft iron

Cold rolled grain oriented steel

Copper alloy

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Question 9 of 35

9. Why are ferrite cores used in radio receivers?

Reduce constant losses

Reduce electric interference

Improve sound quality

Increase receiver efficiency

Question 9 of 35

Question 10 of 35

10. 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 10 of 35

Question 11 of 35

11. 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 11 of 35

Question 12 of 35

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

Open circuit condition

Overloading condition

Moisture presence

High temperature condition

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Question 13 of 35

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

To obtain required voltage ratio

To offer high inductance

To stabilize input/output voltage

To regulate primary current

Question 13 of 35

Question 14 of 35

14. What is this power transformer component called?

Tap charger

Explosion vent

Breather

Buchholz relay

Question 14 of 35

Question 15 of 35

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

Sodium chloride

Ammonium chloride

Silica gel

Charcoal-salt mixture

Question 15 of 35

Question 16 of 35

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

Self induced EMF

Dynamically induced EMF

Statically induced EMF

Mutually induced EMF

Question 16 of 35

Question 17 of 35

17. 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 18 of 35

18. How is moisture controlled in transformer breathers?

Silica gel

Transformer oil

Ammonium jelly

Sodium chloride

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Question 19 of 35

19. Which transformer measures high voltage installations?

Ignition transformers

Potential transformers

Pulse transformers

Constant voltage transformers

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Question 20 of 35

20. What is the cooling method of transformers?

Oil natural water forced cooling

Oil natural cooling

Oil natural air forced cooling

Oil forced air forced cooling

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Question 21 of 35

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

Copper loss

Eddy current loss

Windage loss

Hysteresis loss

Question 21 of 35

Question 22 of 35

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

Oil forced air forced

Oil natural air natural

Air natural

Oil natural air blast

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Question 23 of 35

23. Why are laminated cores used in transformers?

Reduce hysteresis loss

Reduce eddy current loss

Reduce copper loss

Reduce mechanical loss

Question 23 of 35

Question 24 of 35

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

Moisture

Acidity

Dielectric strength

Viscosity

Question 24 of 35

Question 25 of 35

25. What type of transformer is this?

Auto transformer

Core type transformer

Audio frequency transformer

Shell type transformer

Question 25 of 35

Question 26 of 35

26. How is copper loss determined in transformers?

Open circuit test

Impulse test

Short circuit test

Ratio test

Question 26 of 35

Question 27 of 35

27. 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 28 of 35

28. What is the disadvantage of auto transformers?

Heavier weight

Poor voltage regulation

More losses

Cannot isolate secondary winding

Question 28 of 35

Question 29 of 35

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

Reduces eddy current loss

Reduces core space

Minimizes copper use

Reduces hysteresis loss

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Question 30 of 35

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

95% steel, 5% silicon

93% steel, 7% silicon

97% steel, 3% silicon

90% steel, 10% silicon

Question 30 of 35

Question 31 of 35

31. What is absolutely essential for parallel transformer operation?

Type of cooling

Phase sequence

Insulation class

Nature of load

Question 31 of 35

Question 32 of 35

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

7.20%

8.30%

8.71%

9.09%

Question 32 of 35

Question 33 of 35

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

Reduced core thickness

Grain oriented core

Laminated core

Stepped core arrangement

Question 33 of 35

Question 34 of 35

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

To minimize reading errors

To maintain constant output

To minimize the burden

To prevent high static shield

Question 34 of 35

Question 35 of 35

35. How can potential transformer reading errors be reduced?

Using high flux density material

Providing long magnetic path

Using good quality core material

Using thin laminated core

Question 35 of 35