Question 1 of 35

1. What is absolutely essential for parallel transformer operation?

Phase sequence

Insulation class

Type of cooling

Nature of load

Question 1 of 35

Question 2 of 35

2. What is the disadvantage of auto transformers?

Poor voltage regulation

More losses

Cannot isolate secondary winding

Heavier weight

Question 2 of 35

Question 3 of 35

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

Oil natural air blast

Air natural

Oil forced air forced

Oil natural air natural

Question 3 of 35

Question 4 of 35

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

Protection from overloading and short circuits

Protection from tank pressure

Protection from high temperature

Protection from moisture in oil

Question 4 of 35

Question 5 of 35

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

Acidity

Dielectric strength

Viscosity

Moisture

Question 5 of 35

Question 6 of 35

6. How is moisture controlled in transformer breathers?

Silica gel

Transformer oil

Ammonium jelly

Sodium chloride

Question 6 of 35

Question 7 of 35

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

Provide electrical isolation for windings

Disconnect diverter moving contact

Avoid heavy sparking at contacts

Disconnect tappings from neutral

Question 7 of 35

Question 8 of 35

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

Ring core transformer

Silicon steel core transformer

Ferrite core transformer

Grain oriented core transformer

Question 8 of 35

Question 9 of 35

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

Cold rolled grain oriented steel

Rolled steel

Copper alloy

Soft iron

Question 9 of 35

Question 10 of 35

10. How is copper loss determined in transformers?

Open circuit test

Impulse test

Ratio test

Short circuit test

Question 10 of 35

Question 11 of 35

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

Statically induced EMF

Dynamically induced EMF

Mutually induced EMF

Self induced EMF

Question 11 of 35

Question 12 of 35

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

Moisture releasing

Heat releasing

Pressure releasing

Air releasing

Question 12 of 35

Question 13 of 35

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

Transfers heat to atmosphere

Prevents moisture entry

Allows oil expansion due to load variation

Releases internal pressure

Question 13 of 35

Question 14 of 35

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

To minimize reading errors

To prevent high static shield

To maintain constant output

To minimize the burden

Question 14 of 35

Question 15 of 35

15. What type of transformer is this?

Ring core transformer

Air core transformer

Ferrite core transformer

Iron core transformer

Question 15 of 35

Question 16 of 35

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

97% steel, 3% silicon

90% steel, 10% silicon

93% steel, 7% silicon

95% steel, 5% silicon

Question 16 of 35

Question 17 of 35

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

High temperature condition

Overloading condition

Open circuit condition

Moisture presence

Question 17 of 35

Question 18 of 35

18. 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 18 of 35

Question 19 of 35

19. What is the cooling method of transformers?

Oil natural cooling

Oil forced air forced cooling

Oil natural air forced cooling

Oil natural water forced cooling

Question 19 of 35

Question 20 of 35

20. Why are laminated cores used in transformers?

Reduce copper loss

Reduce hysteresis loss

Reduce mechanical loss

Reduce eddy current loss

Question 20 of 35

Question 21 of 35

21. Which transformer measures high voltage installations?

Constant voltage transformers

Pulse transformers

Potential transformers

Ignition transformers

Question 21 of 35

Question 22 of 35

22. Why are ferrite cores used in radio receivers?

Reduce electric interference

Improve sound quality

Increase receiver efficiency

Reduce constant losses

Question 22 of 35

Question 23 of 35

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

Copper loss

Eddy current loss only

Core loss

Hysteresis loss only

Question 23 of 35

Question 24 of 35

24. 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 24 of 35

Question 25 of 35

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

Minimizes copper use

Reduces core space

Reduces hysteresis loss

Reduces eddy current loss

Question 25 of 35

Question 26 of 35

26. 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%

Question 26 of 35

Question 27 of 35

27. What is this power transformer component called?

Breather

Tap charger

Buchholz relay

Explosion vent

Question 27 of 35

Question 28 of 35

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

Optimize for maximum efficiency

Change distribution voltage ratio

Maintain primary voltage

Maintain secondary voltage

Question 28 of 35

Question 29 of 35

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

Maintain constant voltage

Facilitate 3-phase 4-wire distribution

Reduce transformer losses

Avoid overloading

Question 29 of 35

Question 30 of 35

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

Charcoal-salt mixture

Silica gel

Sodium chloride

Ammonium chloride

Question 30 of 35

Question 31 of 35

31. What type of transformer is this?

Auto transformer

Core type transformer

Shell type transformer

Audio frequency transformer

Question 31 of 35

Question 32 of 35

32. 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 32 of 35

Question 33 of 35

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

Reduced core thickness

Grain oriented core

Laminated core

Stepped core arrangement

Question 33 of 35

Question 34 of 35

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

Hysteresis loss

Windage loss

Copper loss

Eddy current loss

Question 34 of 35

Question 35 of 35

35. What condition gives maximum transformer efficiency?

Copper loss < Iron loss

Copper loss = Eddy current loss

Copper loss = Iron loss

Copper loss > Iron loss

Question 35 of 35