Question 1 of 35

1. 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 1 of 35

Question 2 of 35

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

Eddy current loss

Copper loss

Hysteresis loss

Windage loss

Question 2 of 35

Question 3 of 35

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

Protection from moisture in oil

Protection from overloading and short circuits

Protection from high temperature

Protection from tank pressure

Question 3 of 35

Question 4 of 35

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

Air releasing

Moisture releasing

Pressure releasing

Heat releasing

Question 4 of 35

Question 5 of 35

5. 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 regulate primary current

To offer high inductance

Question 5 of 35

Question 6 of 35

6. Why are ferrite cores used in radio receivers?

Increase receiver efficiency

Reduce electric interference

Improve sound quality

Reduce constant losses

Question 6 of 35

Question 7 of 35

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

Moisture presence

Overloading condition

Open circuit condition

High temperature condition

Question 7 of 35

Question 8 of 35

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

Maintain primary voltage

Optimize for maximum efficiency

Maintain secondary voltage

Change distribution voltage ratio

Question 8 of 35

Question 9 of 35

9. Which transformer measures high voltage installations?

Constant voltage transformers

Ignition transformers

Potential transformers

Pulse transformers

Question 9 of 35

Question 10 of 35

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

Ammonium chloride

Charcoal-salt mixture

Silica gel

Sodium chloride

Question 10 of 35

Question 11 of 35

11. What is the disadvantage of auto transformers?

Cannot isolate secondary winding

More losses

Heavier weight

Poor voltage regulation

Question 11 of 35

Question 12 of 35

12. How is copper loss determined in transformers?

Impulse test

Short circuit test

Open circuit test

Ratio test

Question 12 of 35

Question 13 of 35

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

Facilitate 3-phase 4-wire distribution

Avoid overloading

Maintain constant voltage

Reduce transformer losses

Question 13 of 35

Question 14 of 35

14. What condition gives maximum transformer efficiency?

Copper loss > Iron loss

Copper loss < Iron loss

Copper loss = Iron loss

Copper loss = Eddy current loss

Question 14 of 35

Question 15 of 35

15. How is moisture controlled in transformer breathers?

Silica gel

Ammonium jelly

Sodium chloride

Transformer oil

Question 15 of 35

Question 16 of 35

16. What is this power transformer component called?

Explosion vent

Buchholz relay

Tap charger

Breather

Question 16 of 35

Question 17 of 35

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

Avoid heavy sparking at contacts

Disconnect tappings from neutral

Disconnect diverter moving contact

Provide electrical isolation for windings

Question 17 of 35

Question 18 of 35

18. What type of transformer is this?

Audio frequency transformer

Shell type transformer

Core type transformer

Auto transformer

Question 18 of 35

Question 19 of 35

19. How can potential transformer reading errors be reduced?

Using thin laminated core

Providing long magnetic path

Using high flux density material

Using good quality core material

Question 19 of 35

Question 20 of 35

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

Air natural

Oil natural air natural

Oil forced air forced

Oil natural air blast

Question 20 of 35

Question 21 of 35

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

Allows oil expansion due to load variation

Releases internal pressure

Transfers heat to atmosphere

Prevents moisture entry

Question 21 of 35

Question 22 of 35

22. What type of transformer is this?

Iron core transformer

Ferrite core transformer

Ring core transformer

Air core transformer

Question 22 of 35

Question 23 of 35

23. What is absolutely essential for parallel transformer operation?

Phase sequence

Insulation class

Nature of load

Type of cooling

Question 23 of 35

Question 24 of 35

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

Silicon steel core transformer

Ferrite core transformer

Ring core transformer

Grain oriented core transformer

Question 24 of 35

Question 25 of 35

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

8.30%

8.71%

7.20%

9.09%

Question 25 of 35

Question 26 of 35

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

Acidity

Moisture

Dielectric strength

Viscosity

Question 26 of 35

Question 27 of 35

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

Cold rolled grain oriented steel

Soft iron

Rolled steel

Copper alloy

Question 27 of 35

Question 28 of 35

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

Grain oriented core

Stepped core arrangement

Reduced core thickness

Laminated core

Question 28 of 35

Question 29 of 35

29. 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 29 of 35

Question 30 of 35

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

Reduces core space

Minimizes copper use

Reduces hysteresis loss

Reduces eddy current loss

Question 30 of 35

Question 31 of 35

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

Copper loss

Core loss

Hysteresis loss only

Eddy current loss only

Question 31 of 35

Question 32 of 35

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

90% steel, 10% silicon

93% steel, 7% silicon

97% steel, 3% silicon

95% steel, 5% silicon

Question 32 of 35

Question 33 of 35

33. Why are laminated cores used in transformers?

Reduce eddy current loss

Reduce hysteresis loss

Reduce mechanical loss

Reduce copper loss

Question 33 of 35

Question 34 of 35

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

To maintain constant output

To prevent high static shield

To minimize the burden

To minimize reading errors

Question 34 of 35

Question 35 of 35

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

Self induced EMF

Mutually induced EMF

Statically induced EMF

Dynamically induced EMF

Question 35 of 35