51. Buchholz relay is used on
a. Air cooled transformers
b. Oil cooled transformers
c. Welding transformers
d. Funtace transformers
52. Buchholz relay is generally not provided on transformer below
a. 1 KVA
2. 5 KVA
c. 50 kVA
d. 500 KVA
53. Operating time of buchholz relay is of the orderof
a. 0.1 micro second
b. 0.1 milli second
c. 0..1 second
d. 1 second
54. In a distribution transformer , normally
a. core losses are equal to copper losses
b. core losses are more than copper losses
c. core losses are less than copper losses
d. core losses are half of the copper losses
55. A buchholz relay will operate in a transformer whenever there is
a. large internal fault
b. saturation of magnetic current
c. over load
d. any of the above
56. Which of the following protection is normally not provided on small distribution transformers
a. Over current protection
b. Buchholz relay
c. Over fluxing protection
d. All of the above
57. For a transformer , operating at constant load current. maximum efficiency will occur at
a. Zero power factor
b. Unity power factor
c. 0.8 leading power factor
d. 0.8 lagging power factor
58. The function of a breather in a transformer is
a. to provide protection against over currents
b. to suppress harmonics
c. to arrest flow of moisture into the tank
d. to control the level of oil in the tank
59. The efficiency of a 430/200 V transformer at full load 0.8 p.f leading will be
a. 99%
b. 95.5%
c. 95%
d. 90%
60. A good voltage regulation of a transformer means
a. difference between primary and secondary voltage is least
b. difference between primary and secondary voltage is maximum
c. Output voltage fluctuation from no load to full load is least
d. Output voltage fluctuation with power factor is the least
