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) A distribution transformer is selected on the basis of
A) voltage regulation
B) efficiency
C) all day efficiency
D) none of these
Ans:C
2) The distribution transformers are designed with minimum possible iron losses. This is because
A) the primary of a distribution transformer is energized for all the 24 hours
B) iron losses will cause undue heating
C) the iron losses may cause damage to the insulation
D) none of the above
Ans:A
3) 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:A
4) Transformers are rated in KVA instead of KW because
A) load pf is often not known
B) KVA is fixed where KW depends on load pf
C) total transformer loss depends on volt-amperes
D) it has become customary
Ans:C
5) Which of the following methods is employed for cooling of power transformer of rating not exceeding 10 MVA
A) Air blast cooling
B) Natural oil cooling
C) Forced oil cooling
D) Natural oil cooling
Ans:B
6) Distribution transformers are designed to have maximum efficiency nearly at ......... of full load
A) 100%
B) 70%
C) 25%
D) 10%
Ans:B
7) Which is the arrangement of winding in a core type single phase transformer?
A) Half lv side and half hv outside on each core limb
B) Lv on one core limb and hv on the other
C) sandwiched lv and hv discs on each core limb
D) Half hv inside and half hv outside on each core limb
Ans:A
8) The open circuit test on a transformer is usually performed by exciting the low voltage winding. This is because
A) it draws sufficiently large no-load current which can be conveniently measured
B) The required power input is low
C) it is not advisable to work on high voltage side
D) the voltage required is low
Ans:A
9) A 500 KVA transformer has constant loss of 500 W and copper losses at full load are 2000W. Then at what load is the efficiency maximum?
A) 250 KVA
B) 500 KVA
C) 1000 KVA
D) 125 KVA
Ans:A
10) A 20 KVA, 2000/200 V , 1-phase transformer has name plate leakage impedance of 8%. voltage required to be applied on the high voltage side to circulate full-load current with the low voltage winding short circuited will be
A) 16 V
B) 56.66 V
C) 160 V
D) 568.68 V
Ans:C
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