ELECTRICIAN 1st YEAR MODULE -Transformer

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

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Question 2 of 35

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

Silica gel

Sodium chloride

Ammonium chloride

Charcoal-salt mixture

Question 2 of 35

Question 3 of 35

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

Soft iron

Copper alloy

Cold rolled grain oriented steel

Rolled steel

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Question 4 of 35

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

Protection from high temperature

Protection from overloading and short circuits

Protection from moisture in oil

Protection from tank pressure

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Question 5 of 35

5. What type of transformer is this?

Audio frequency transformer

Shell type transformer

Auto transformer

Core type transformer

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Question 6 of 35

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

90% steel, 10% silicon

97% steel, 3% silicon

93% steel, 7% silicon

95% steel, 5% silicon

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Question 7 of 35

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

Dynamically induced EMF

Self induced EMF

Statically induced EMF

Mutually induced EMF

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Question 8 of 35

8. What is this power transformer component called?

Buchholz relay

Tap charger

Breather

Explosion vent

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Question 9 of 35

9. How is moisture controlled in transformer breathers?

Ammonium jelly

Sodium chloride

Transformer oil

Silica gel

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Question 10 of 35

10. 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

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Question 11 of 35

11. What type of transformer is this?

Iron core transformer

Ring core transformer

Air core transformer

Ferrite core transformer

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Question 12 of 35

12. 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

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Question 13 of 35

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

Eddy current loss only

Core loss

Hysteresis loss only

Copper loss

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Question 14 of 35

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

To maintain constant output

To prevent high static shield

To minimize reading errors

To minimize the burden

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Question 15 of 35

15. Why are ferrite cores used in radio receivers?

Reduce constant losses

Reduce electric interference

Improve sound quality

Increase receiver efficiency

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Question 16 of 35

16. Why are laminated cores used in transformers?

Reduce hysteresis loss

Reduce copper loss

Reduce mechanical loss

Reduce eddy current loss

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Question 17 of 35

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

8.71%

8.30%

9.09%

7.20%

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Question 18 of 35

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

Minimizes copper use

Reduces hysteresis loss

Reduces eddy current loss

Reduces core space

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Question 19 of 35

19. Which transformer measures high voltage installations?

Pulse transformers

Constant voltage transformers

Potential transformers

Ignition transformers

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Question 20 of 35

20. What is absolutely essential for parallel transformer operation?

Nature of load

Phase sequence

Type of cooling

Insulation class

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Question 21 of 35

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

Moisture presence

Open circuit condition

High temperature condition

Overloading condition

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Question 22 of 35

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

Ring core transformer

Ferrite core transformer

Silicon steel core transformer

Grain oriented core transformer

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Question 23 of 35

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

Reduce transformer losses

Avoid overloading

Maintain constant voltage

Facilitate 3-phase 4-wire distribution

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Question 24 of 35

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

Oil natural air natural

Oil natural air blast

Air natural

Oil forced air forced

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Question 25 of 35

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

Change distribution voltage ratio

Optimize for maximum efficiency

Maintain secondary voltage

Maintain primary voltage

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Question 26 of 35

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

Disconnect tappings from neutral

Avoid heavy sparking at contacts

Provide electrical isolation for windings

Disconnect diverter moving contact

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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. Which construction technique reduces copper loss in large transformers?

Stepped core arrangement

Grain oriented core

Laminated core

Reduced core thickness

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Question 29 of 35

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

Air releasing

Moisture releasing

Pressure releasing

Heat releasing

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Question 30 of 35

30. What is the cooling method of transformers?

Oil natural water forced cooling

Oil forced air forced cooling

Oil natural cooling

Oil natural air forced cooling

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Question 31 of 35

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

To regulate primary current

To obtain required voltage ratio

To offer high inductance

To stabilize input/output voltage

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Question 32 of 35

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

Moisture

Acidity

Dielectric strength

Viscosity

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Question 33 of 35

33. How is copper loss determined in transformers?

Open circuit test

Ratio test

Impulse test

Short circuit test

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Question 34 of 35

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

Hysteresis loss

Windage loss

Copper loss

Eddy current loss

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Question 35 of 35

35. What is the disadvantage of auto transformers?

More losses

Heavier weight

Poor voltage regulation

Cannot isolate secondary winding

Question 35 of 35