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MCQs

Total Questions : 631 | Page 5 of 64 pages
Question 41. Iron loss of a transformer can be measured by
  1.    low power factor wattmeter
  2.    unity power factor wattmeter
  3.    frequency meter
  4.    any type of wattmeter
 Discuss Question
Answer: Option A. -> low power factor wattmeter
Question 42. Which of the following property is not necessarily desirable in the material for transformer core?
  1.    Mechanical strength
  2.    Low hysteresis loss
  3.    High thermal conductivity
  4.    High permeability
 Discuss Question
Answer: Option C. -> High thermal conductivity
Question 43. Efficiency of a power transformer is of the order of
  1.    100 per cent
  2.    98 per cent
  3.    50 per cent
  4.    25 per cent
 Discuss Question
Answer: Option B. -> 98 per cent
Question 44. Which of the following properties is not necessarily desirable for the material for transformer core?
  1.    Low hysteresis loss
  2.    High permeability
  3.    High thermal conductivity
  4.    Adequate mechanical strength
 Discuss Question
Answer: Option C. -> High thermal conductivity
Question 45. Natural air cooling is generally restricted for transformers up to
  1.    1.5 MVA
  2.    5 MVA
  3.    15 MVA
  4.    50 MVA
 Discuss Question
Answer: Option A. -> 1.5 MVA
Question 46. Reduction in core losses and increase in permeability are obtained with transformer employing
  1.    core built-up of laminations of cold rolled grain oriented steel
  2.    core built-up of laminations of hot rolled sheet
  3.    either of the above
  4.    none of the above
 Discuss Question
Answer: Option A. -> core built-up of laminations of cold rolled grain oriented steel
Question 47. Harmonics in transformer result in
  1.    increased core losses
  2.    increased I2R losses
  3.    magnetic interference with communication circuits
  4.    all of the above
 Discuss Question
Answer: Option D. -> all of the above
Question 48. The efficiency of a transformer, under heavy loads, is comparatively low because
  1.    copper loss becomes high in proportion to the output
  2.    iron loss is increased considerably
  3.    voltage drop both in primary and secondary becomes large
  4.    secondary output is much less as compared to primary input
 Discuss Question
Answer: Option A. -> copper loss becomes high in proportion to the output
Question 49. In a power or distribution transformer about 10 per cent end turns are heavily insulated
  1.    to withstand the high voltage drop due to line surge produced by the shunting capacitance of the end turns
  2.    to absorb the line surge voltage and save the winding of transformer from damage
  3.    to reflect the line surge and save the winding of a transformer from damage
  4.    none of the above
 Discuss Question
Answer: Option A. -> to withstand the high voltage drop due to line surge produced by the shunting capacitance of the end turns
Question 50. Which winding in a transformer has more number of turns?
  1.    Low voltage winding
  2.    High voltage winding
  3.    Primary winding
  4.    Secondary winding
 Discuss Question
Answer: Option B. -> High voltage winding

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