Question 1 of 35

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

Change distribution voltage ratio

Maintain secondary voltage

Optimize for maximum efficiency

Maintain primary voltage

Question 1 of 35

Question 2 of 35

2. What condition gives maximum transformer efficiency?

Copper loss = Eddy current loss

Copper loss > Iron loss

Copper loss < Iron loss

Copper loss = Iron loss

Question 2 of 35

Question 3 of 35

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

Eddy current loss only

Core loss

Hysteresis loss only

Copper loss

Question 3 of 35

Question 4 of 35

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

93% steel, 7% silicon

95% steel, 5% silicon

97% steel, 3% silicon

90% steel, 10% silicon

Question 4 of 35

Question 5 of 35

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

Disconnect diverter moving contact

Provide electrical isolation for windings

Disconnect tappings from neutral

Avoid heavy sparking at contacts

Question 5 of 35

Question 6 of 35

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

Ring core transformer

Ferrite core transformer

Silicon steel core transformer

Grain oriented core transformer

Question 6 of 35

Question 7 of 35

7. Why are ferrite cores used in radio receivers?

Reduce constant losses

Reduce electric interference

Increase receiver efficiency

Improve sound quality

Question 7 of 35

Question 8 of 35

8. 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 obtain required voltage ratio

To regulate primary current

Question 8 of 35

Question 9 of 35

9. How is moisture controlled in transformer breathers?

Ammonium jelly

Silica gel

Transformer oil

Sodium chloride

Question 9 of 35

Question 10 of 35

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

Reduce transformer losses

Avoid overloading

Facilitate 3-phase 4-wire distribution

Maintain constant voltage

Question 10 of 35

Question 11 of 35

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

Oil natural air blast

Oil forced air forced

Oil natural air natural

Air natural

Question 11 of 35

Question 12 of 35

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

Heat releasing

Air releasing

Moisture releasing

Pressure releasing

Question 12 of 35

Question 13 of 35

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

Silica gel

Sodium chloride

Ammonium chloride

Charcoal-salt mixture

Question 13 of 35

Question 14 of 35

14. How can potential transformer reading errors be reduced?

Using high flux density material

Using thin laminated core

Providing long magnetic path

Using good quality core material

Question 14 of 35

Question 15 of 35

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

Overloading condition

High temperature condition

Open circuit condition

Moisture presence

Question 15 of 35

Question 16 of 35

16. Why are laminated cores used in transformers?

Reduce mechanical loss

Reduce copper loss

Reduce eddy current loss

Reduce hysteresis loss

Question 16 of 35

Question 17 of 35

17. What type of transformer is this?

Iron core transformer

Ring core transformer

Air core transformer

Ferrite core transformer

Question 17 of 35

Question 18 of 35

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

Stepped core arrangement

Laminated core

Grain oriented core

Reduced core thickness

Question 18 of 35

Question 19 of 35

19. 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 19 of 35

Question 20 of 35

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

Releases internal pressure

Prevents moisture entry

Allows oil expansion due to load variation

Transfers heat to atmosphere

Question 20 of 35

Question 21 of 35

21. 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

Question 21 of 35

Question 22 of 35

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

Self induced EMF

Dynamically induced EMF

Mutually induced EMF

Statically induced EMF

Question 22 of 35

Question 23 of 35

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

Rolled steel

Soft iron

Copper alloy

Cold rolled grain oriented steel

Question 23 of 35

Question 24 of 35

24. What type of transformer is this?

Audio frequency transformer

Core type transformer

Auto transformer

Shell type transformer

Question 24 of 35

Question 25 of 35

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

Protection from moisture in oil

Protection from tank pressure

Protection from overloading and short circuits

Protection from high temperature

Question 25 of 35

Question 26 of 35

26. What is the cooling method of transformers?

Oil forced air forced cooling

Oil natural cooling

Oil natural air forced cooling

Oil natural water forced cooling

Question 26 of 35

Question 27 of 35

27. Which transformer measures high voltage installations?

Pulse transformers

Constant voltage transformers

Potential transformers

Ignition transformers

Question 27 of 35

Question 28 of 35

28. 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%

Question 28 of 35

Question 29 of 35

29. How is copper loss determined in transformers?

Ratio test

Open circuit test

Short circuit test

Impulse test

Question 29 of 35

Question 30 of 35

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

Reduces hysteresis loss

Reduces eddy current loss

Reduces core space

Minimizes copper use

Question 30 of 35

Question 31 of 35

31. What is absolutely essential for parallel transformer operation?

Insulation class

Type of cooling

Nature of load

Phase sequence

Question 31 of 35

Question 32 of 35

32. What is this power transformer component called?

Tap charger

Buchholz relay

Breather

Explosion vent

Question 32 of 35

Question 33 of 35

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

Dielectric strength

Moisture

Viscosity

Acidity

Question 33 of 35

Question 34 of 35

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

Copper loss

Eddy current loss

Hysteresis loss

Windage loss

Question 34 of 35

Question 35 of 35

35. What is the disadvantage of auto transformers?

Heavier weight

Poor voltage regulation

More losses

Cannot isolate secondary winding

Question 35 of 35