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) Core of large power transformers are made from which one of the following?
A) Hot-rolled steel
B) Cold-rolled non grain oriented steel
C) Cold-rolled grain oriented steel
D) ferrite
Ans:C
2) Which of the following will improve the mutual coupling between primary and secondary circuits?
A) Transformer oil of high breakdown voltage
B) High reluctance magnetic core
C) Winding material of high resistivity
D) Low reluctance magnetic core
Ans:D
3) The joints in the transformer core lamination are staggered so as to
A) avoid continuous gap causing increase in magnetizing current
B) increase the magnetic strength of the assembled core
C) avoid undue humming noise
D) facilitate assembly of core after putting preformed coils on the core
E) all of the above
Ans:E
4) What does the use of higher flux density value in a transformer design lead to?
A) Increase in weight per KVA
B) Decrease in weight per KVA
C) Reduced iron losses
D) Reduced copper losses
Ans:B
5) The yoke sections of transformer employing hot rolled lamination is made 15 percent more than that of core in order to
A) reduce the copper losses
B) reduce the magnetizing current and iron loss in yoke
C) provide better cooling
D) all of the above
Ans:B
6) In a large capacity transformer, 5% of the turns at the end of hv winding are provided with extra insulation so as to provide protection
A) against corona
B) against lightening
C) due to surges occurring during switching operations
D) all of the above
Ans:C
7) Low voltage winding are placed next to the core in the case of concentric winding as in this case................ is reduced
A) hysteresis loss
B) leakage fluxes
C) eddy current loss
D) copper loss
E) insulation requirement
Ans:E
8) The winding used in a 3-phase shell type transformer is ................ type
A) circular
B) cylindrical
C) sandwich
D) rectangular
Ans:C
9) Spiral core transformer, in which core is made up of steel strip has the advantage of
A) minimum losses
B) lighter construction
C) lesser weight
D) all of these
Ans:D
10) Sludge formation in transformer oil is due to which one of the following?
A) Ingress of dust particles and moisture in the oil
B) Appearance of small fragments of paper, varnish, cotton and other organic materials in the oil
C) Chemical reaction of transformer oil with the insulating materials
D) Oxidation of transformer oil
Ans:D
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