Hi friends, this post is about transformer objectives. These are some of the questions asked in previous question papers of Gate, IES and other competitive exams. check out and comment if you have any doubts.....
1) Transformer core laminations are coated with an enamel layer in order to
A) reduce hum
B) attain adhesion between laminations
C) insulate laminations from each other
D) prevent corrosion of the laminations
Ans:C
2) Grain oriented laminated sheet steel in transformer reduces
A) copper loss
B) eddy current loss
C) hysteresis loss
D) none of the above
Ans:C
3) The permissible flux density in cold rolled grain oriented steel is about
A) 1.8 T
B) 2.5 T
C) 3.5 T
D) 4.5 T
Ans:A
4) Why is the core of the transformer built up of laminations?
A) To reduce eddy current losses
B) For convenience of fabrication
C) No specific advantage
D) For increasing the permeability
Ans:A
5) The degree of mechanical vibrations caused by core laminations in a transformer depends on
A) size of laminations
B) gauge of laminations
C) tightness of clamping
D) all of the above
Ans:D
6) The size of the transformer core depends upon
A) frequency
B) permissible flux density in the core material
C) area of the core
D) both (A) and (B)
Ans:D
7) The all day efficiency of a distribution transformer will be high with low
A) copper losses
B) iron losses
C) operating temperature
D) copper as well as iron losses
Ans:B
8) In order to reduce the hysteresis loss
A) core may be laminated
B) silicon steel may be used as the core material
C) core may be constructed with any permanent magnet material such as Alnico
D) core may be impregnated with varnish
Ans:B
9) If the iron core of a transformer is replaced by an air core, then the hysteresis losses in the transformer will
A) increase
B) decrease
C) remain unchanged
D) become zero
Ans:D
10) The all day efficiency of a transformer depends primarily on
A) its copper loss
B) the amount of load
C) the duration of load
D) both (B) and (C)
Ans:D
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