41. Suitable value of flux density for design of large transformer is
a) 1.1 T
b) 1.4 T
c) 1.6 T
d) 1.9 T
ans. c
42. An iron cored transformer is working at a maximum flux density of 0.8 wb/m-sq.Its core is replaced by silicon steel core, working at a maximum flux density of 1.2 wb/m-sq. If total flux is to remain the same , what is the reduction in volume expressed as a percentage of the original volume? The frequency and voltage per turn are the same in both sides
a) 33 %
b) 9 %
c) 22 %
d) 11 %
ans. a
43. Tappings of a transformer are provided
a) at the phase end of lv side
b) at the phase end of hv side
c) at the neutral end of hv side
d) at the middle of the hv side.
ans. d
44. Under short-circuit conditions the windings of a transformer having 5% impedance will experience a radial force
a) 5 times of full load value
b) 20 times of full load value
c) 25 times of full load value
d) 400 times the full load value
ans. d
45. Addition of tubes to the transformer tank improves heat dissipation capacity because of
a) additional cooling surface
b) additional dissipation by radiation only
c) additional dissipation by convection only
d) additional dissipation by radiation and convection both.
ans. d
46. For a pulse transformer , the material used for its core and the possible turns ratio from primary to secondary are respectively as
a) ferrite; 20 : 1
b) ferrite; 1:1
c) laminated iron ; 1:1
d) powered iron; 1:1
ans.b
47. Heat dissipation by radiation in oil immersed transformers with cooling tubes is
a) about 0.6 Watt/metre-sq/degree centigrade
b) about 2 Watt/metre-sq/degree centigrade
c) about 10 Watt/metre-sq/degree centigrade
d) about 50 Watt/metre-sq/degree centigrade
ans. a
48. The slot leakage flux is more in case of
a) open type of slots
b) semi-closed slots
c) closed slots
d) open slots with aluminium conductors
ans. c
49. An ac winding has 2 slots per pole per phase. The slot harmonics will be
a) 5th and 7th
b) 11th and 13 th
c) 17th and 19th
d) none of the above.
ans. b
50. If m is the slots per pole/phase and A is any integer, then what order harmonics will have the same distribution factor as the fundamental
a) 6 Am+or- 1
b) 6 A+ or -m
c) 6 m+or-A
d) none of the above
ans. d
a) 1.1 T
b) 1.4 T
c) 1.6 T
d) 1.9 T
ans. c
42. An iron cored transformer is working at a maximum flux density of 0.8 wb/m-sq.Its core is replaced by silicon steel core, working at a maximum flux density of 1.2 wb/m-sq. If total flux is to remain the same , what is the reduction in volume expressed as a percentage of the original volume? The frequency and voltage per turn are the same in both sides
a) 33 %
b) 9 %
c) 22 %
d) 11 %
ans. a
43. Tappings of a transformer are provided
a) at the phase end of lv side
b) at the phase end of hv side
c) at the neutral end of hv side
d) at the middle of the hv side.
ans. d
44. Under short-circuit conditions the windings of a transformer having 5% impedance will experience a radial force
a) 5 times of full load value
b) 20 times of full load value
c) 25 times of full load value
d) 400 times the full load value
ans. d
45. Addition of tubes to the transformer tank improves heat dissipation capacity because of
a) additional cooling surface
b) additional dissipation by radiation only
c) additional dissipation by convection only
d) additional dissipation by radiation and convection both.
ans. d
46. For a pulse transformer , the material used for its core and the possible turns ratio from primary to secondary are respectively as
a) ferrite; 20 : 1
b) ferrite; 1:1
c) laminated iron ; 1:1
d) powered iron; 1:1
ans.b
47. Heat dissipation by radiation in oil immersed transformers with cooling tubes is
a) about 0.6 Watt/metre-sq/degree centigrade
b) about 2 Watt/metre-sq/degree centigrade
c) about 10 Watt/metre-sq/degree centigrade
d) about 50 Watt/metre-sq/degree centigrade
ans. a
48. The slot leakage flux is more in case of
a) open type of slots
b) semi-closed slots
c) closed slots
d) open slots with aluminium conductors
ans. c
49. An ac winding has 2 slots per pole per phase. The slot harmonics will be
a) 5th and 7th
b) 11th and 13 th
c) 17th and 19th
d) none of the above.
ans. b
50. If m is the slots per pole/phase and A is any integer, then what order harmonics will have the same distribution factor as the fundamental
a) 6 Am+or- 1
b) 6 A+ or -m
c) 6 m+or-A
d) none of the above
ans. d
No comments:
Post a Comment