ELECTRICIAN 1st YEAR MODULE -Transformer

Question 1 of 35

1. Why are laminated cores used in transformers?

Reduce hysteresis loss

Reduce mechanical loss

Reduce eddy current loss

Reduce copper loss

Question 1 of 35

Question 2 of 35

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

Mutually induced EMF

Self induced EMF

Statically induced EMF

Dynamically induced EMF

Question 2 of 35

Question 3 of 35

3. What type of transformer is this?

Core type transformer

Audio frequency transformer

Shell type transformer

Auto transformer

Question 3 of 35

Question 4 of 35

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

Dielectric strength

Acidity

Viscosity

Moisture

Question 4 of 35

Question 5 of 35

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

Silicon steel core transformer

Ring core transformer

Grain oriented core transformer

Ferrite core transformer

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Question 6 of 35

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

Transfers heat to atmosphere

Releases internal pressure

Prevents moisture entry

Allows oil expansion due to load variation

Question 6 of 35

Question 7 of 35

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

Windage loss

Hysteresis loss

Copper loss

Eddy current loss

Question 7 of 35

Question 8 of 35

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

Provide electrical isolation for windings

Disconnect diverter moving contact

Disconnect tappings from neutral

Avoid heavy sparking at contacts

Question 8 of 35

Question 9 of 35

9. What is the cooling method of transformers?

Oil natural cooling

Oil natural water forced cooling

Oil forced air forced cooling

Oil natural air forced cooling

Question 9 of 35

Question 10 of 35

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

Air releasing

Pressure releasing

Moisture releasing

Heat releasing

Question 10 of 35

Question 11 of 35

11. Why are ferrite cores used in radio receivers?

Increase receiver efficiency

Reduce electric interference

Reduce constant losses

Improve sound quality

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Question 12 of 35

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

Core loss

Copper loss

Hysteresis loss only

Eddy current loss only

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Question 13 of 35

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

To minimize the burden

To prevent high static shield

To maintain constant output

To minimize reading errors

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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:

7.20%

8.30%

8.71%

9.09%

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Question 15 of 35

15. What type of transformer is this?

Ferrite core transformer

Iron core transformer

Air core transformer

Ring core transformer

Question 15 of 35

Question 16 of 35

16. How is moisture controlled in transformer breathers?

Silica gel

Sodium chloride

Ammonium jelly

Transformer oil

Question 16 of 35

Question 17 of 35

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

Maintain secondary voltage

Optimize for maximum efficiency

Change distribution voltage ratio

Maintain primary voltage

Question 17 of 35

Question 18 of 35

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

To offer high inductance

To stabilize input/output voltage

To regulate primary current

To obtain required voltage ratio

Question 18 of 35

Question 19 of 35

19. How is copper loss determined in transformers?

Ratio test

Impulse test

Short circuit test

Open circuit test

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Question 20 of 35

20. What is absolutely essential for parallel transformer operation?

Type of cooling

Nature of load

Phase sequence

Insulation class

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Question 21 of 35

21. What is the disadvantage of auto transformers?

More losses

Cannot isolate secondary winding

Heavier weight

Poor voltage regulation

Question 21 of 35

Question 22 of 35

22. 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 22 of 35

Question 23 of 35

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

Cold rolled grain oriented steel

Rolled steel

Copper alloy

Soft iron

Question 23 of 35

Question 24 of 35

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

Oil natural air blast

Oil natural air natural

Oil forced air forced

Air natural

Question 24 of 35

Question 25 of 35

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

Reduces hysteresis loss

Reduces eddy current loss

Minimizes copper use

Reduces core space

Question 25 of 35

Question 26 of 35

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

Open circuit condition

Moisture presence

Overloading condition

High temperature condition

Question 26 of 35

Question 27 of 35

27. What is this power transformer component called?

Breather

Explosion vent

Tap charger

Buchholz relay

Question 27 of 35

Question 28 of 35

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

Protection from overloading and short circuits

Protection from tank pressure

Protection from moisture in oil

Protection from high temperature

Question 28 of 35

Question 29 of 35

29. What condition gives maximum transformer efficiency?

Copper loss = Eddy current loss

Copper loss = Iron loss

Copper loss > Iron loss

Copper loss < Iron loss

Question 29 of 35

Question 30 of 35

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

Maintain constant voltage

Avoid overloading

Facilitate 3-phase 4-wire distribution

Reduce transformer losses

Question 30 of 35

Question 31 of 35

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

97% steel, 3% silicon

93% steel, 7% silicon

90% steel, 10% silicon

95% steel, 5% silicon

Question 31 of 35

Question 32 of 35

32. Which transformer measures high voltage installations?

Ignition transformers

Constant voltage transformers

Potential transformers

Pulse transformers

Question 32 of 35

Question 33 of 35

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

Sodium chloride

Charcoal-salt mixture

Ammonium chloride

Silica gel

Question 33 of 35

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

Question 34 of 35

Question 35 of 35

35. How can potential transformer reading errors be reduced?

Providing long magnetic path

Using high flux density material

Using thin laminated core

Using good quality core material

Question 35 of 35