ELECTRICIAN 1st YEAR MODULE -Transformer

Question 1 of 35

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

Dynamically induced EMF

Self induced EMF

Mutually induced EMF

Statically induced EMF

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Question 2 of 35

2. Which transformer measures high voltage installations?

Potential transformers

Constant voltage transformers

Ignition transformers

Pulse transformers

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Question 3 of 35

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

Air releasing

Moisture releasing

Heat releasing

Pressure releasing

Question 3 of 35

Question 4 of 35

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

Disconnect tappings from neutral

Provide electrical isolation for windings

Avoid heavy sparking at contacts

Disconnect diverter moving contact

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Question 5 of 35

5. What is the disadvantage of auto transformers?

Poor voltage regulation

Heavier weight

Cannot isolate secondary winding

More losses

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Question 6 of 35

6. What condition gives maximum transformer efficiency?

Copper loss < Iron loss

Copper loss > Iron loss

Copper loss = Eddy current loss

Copper loss = Iron loss

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Question 7 of 35

7. 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

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Question 8 of 35

8. What type of transformer is this?

Core type transformer

Audio frequency transformer

Auto transformer

Shell type transformer

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Question 9 of 35

9. 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 10 of 35

10. 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 11 of 35

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

Reduces hysteresis loss

Minimizes copper use

Reduces core space

Reduces eddy current loss

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Question 12 of 35

12. 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

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Question 13 of 35

13. 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 14 of 35

14. 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 15 of 35

15. 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

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Question 16 of 35

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

Sodium chloride

Charcoal-salt mixture

Ammonium chloride

Silica gel

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Question 17 of 35

17. 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 18 of 35

18. What type of transformer is this?

Iron core transformer

Ferrite core transformer

Ring core transformer

Air core transformer

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Question 19 of 35

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

Oil natural air blast

Oil natural air natural

Air natural

Oil forced air forced

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Question 20 of 35

20. 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 21 of 35

21. Why are laminated cores used in transformers?

Reduce copper loss

Reduce mechanical loss

Reduce eddy current loss

Reduce hysteresis loss

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Question 22 of 35

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

7.20%

8.71%

9.09%

8.30%

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Question 23 of 35

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

Eddy current loss only

Core loss

Copper loss

Hysteresis loss only

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Question 24 of 35

24. What is absolutely essential for parallel transformer operation?

Phase sequence

Insulation class

Nature of load

Type of cooling

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Question 25 of 35

25. Why are ferrite cores used in radio receivers?

Reduce electric interference

Reduce constant losses

Increase receiver efficiency

Improve sound quality

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Question 26 of 35

26. How is copper loss determined in transformers?

Ratio test

Open circuit test

Short circuit test

Impulse test

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Question 27 of 35

27. How is moisture controlled in transformer breathers?

Sodium chloride

Silica gel

Ammonium jelly

Transformer oil

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Question 28 of 35

28. 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 29 of 35

29. 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 30 of 35

30. 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

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Question 31 of 35

31. What is this power transformer component called?

Explosion vent

Buchholz relay

Breather

Tap charger

Question 31 of 35

Question 32 of 35

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

Eddy current loss

Copper loss

Windage loss

Hysteresis loss

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Question 33 of 35

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

Moisture

Acidity

Viscosity

Dielectric strength

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Question 34 of 35

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

Grain oriented core

Stepped core arrangement

Laminated core

Reduced core thickness

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Question 35 of 35

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

Protection from high temperature

Protection from tank pressure

Protection from overloading and short circuits

Protection from moisture in oil

Question 35 of 35