1. A transformer operates
Explain:- A transformer operates at power factor depending on the power factor of the load.
2. In an ideal transformer on no-load , the primary applied voltage is balanced by
Explain:- In an ideal transformer on no-load , the primary applied voltage is balanced by the primary induced emf.
3. The degree of mechanical vibrations produced by the laminations of a transformer depends on
Explain:- The degree of mechanical vibrations produced by the laminations of a transformer depends on all these parameters.
4. The no-load current drawn by transformer is usually what percent of the full-load current ?
Explain:- The no-load current drawn by transformer is usually 2 to 5 percent of the full-load current.
5. In the transformer following winding has got more cross-sectional area
Explain:- In a transformer low voltage winding has more cross-sectional area because low voltage winding has more current than high voltage winding.
6. No-load test on a transformer is carried out to determine
Explain:- No-load test on a transformer is carried out to determine magnetizing current and core loss of the transformer.
7. The dielectric strength of transformer oil is expected to be
Explain:- Minimum breakdown voltage of transformer oil or dielectric strength of transformer oil at which this oil can safely be used in transformer, is considered as 30 kV.
8. A common method of cooling in power transformer is
Explain:- A common method of cooling in power transformer is Oil Cooling.
9. Sumpner's test is conducted on transformers to determine
Explain:- The full load test on a small transformer is very convenient, but on the large transformer, it is very difficult. The maximum temperature rise in a large transformer is determined by the full load test. This test is called, back-to-back test, regenerative test or Sumpner’s test.
10. Transformer breaths in when
Explain:- Transformer breaths in when load decreases.
11. The maximum efficiency of a distribution transformer is
Explain:- The maximum efficiency of a distribution transformer is at 50% of full load.
12. Power transformers are designed to have maximum efficiency at
Explain:- Power transformers are designed to have maximum efficiency at nearly full load.
13. In a transformer routine efficiency depends upon
Explain:- In a transformer routine efficiency depends upon load current and power factor of the load.
14. The permissible flux density in case of cold rolled grain oriented steel is around
Explain:- The permissible flux density in case of cold rolled grain oriented steel is around 1.7 Wb/m2.
15. A transformer oil must be free from
Explain:- A transformer oil must be free from colour, gases, sludge and moisture.
16. The magnetising current of a transformer is usually small because it has
Explain:- The magnetising current of a transformer is usually small because it has small air gap.
17. The main reason for generation of harmonics in a transformer could be
Explain:- The main reason for generation of harmonics in a transformer is due to saturation of core.
18. The path of the magnetic flux in transformer should have
Explain:- The path of the magnetic flux in transformer should have low reluctance.
19. Which of the following property is not necessarily desirable in the material for transformer core ?
Explain:- High thermal conductivity property is not necessarily desirable in the material for transformer core.
20. The thickness of laminations used in a transformer is usually
Explain:- The thickness of laminations used in a transformer is usually 0.4 mm to 0.5 mm.
21. The efficiency of a transformer, under heavy loads, is comparatively low because
Explain:- The efficiency of a transformer, under heavy loads, is comparatively low because copper loss becomes high in proportion to the output .
22. A no-load test is performed on a transformer to determine
Explain:- A no-load test is performed on a transformer to determine core loss(Iron loss) and magnetizing current.
23. Part of the transformer which is most subject to damage from overheating is
Explain:- Part of the transformer which is most subject to damage from overheating is winding insulation.
24. If a transformer is continuously operated the maximum temperature rise will occur in
Explain:- If a transformer is continuously operated the maximum temperature rise will occur in windings because current flows through windings.
25. Auto-transformer makes effective saving of copper and copper losses, when its transformation ratio is
Explain:- Auto-transformer makes effective saving of copper and copper losses, when its transformation ratio is approximately equal to one.
26. Minimum voltage regulation occurs when the power factor of the load is
Explain:- Minimum voltage regulation occurs when the power factor of the load is leading.
27. A good voltage regulation of a transformer means
Explain:- A good voltage regulation of a transformer means output voltage fluctuation from no load to full load is least.
28. The efficiency of two identical transformers under load conditions can be determined by
Explain:- The efficiency of two identical transformers under load conditions can be determined by Back to Back test.
29. A transformer transforms
Explain:- A transformer transforms Electrical Power from one electrical circuit to another electrical circuit without any change in frequency.
30. A shell-type transformer has
Explain:- A shell-type transformer has reduced magnetic leakage.
31. Which of the following protection is normally not provided on small distribution transformers?
Explain:- Buchholz relay is normally not provided on small distribution transformers.
32. Which of the following acts as a protection against high voltage surges due to lightning and switching ?
Explain:- Horn gap acts as a protection against high voltage surges due to lightning and switching.
33. Reduction in core losses and increase in permeability are obtained with transformer employing
Explain:- Reduction in core losses and increase in permeability are obtained with transformer employing core built-up of laminations of cold rolled grain oriented steel.
34. The transformer oil should have _____ volatility and _____ viscosity.
Explain:- The transformer oil should have low volatility and low viscosity.
35. Iron loss of a transformer can be measured by
Explain:- Iron loss of a transformer can be measured by low power factor wattmeter.
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