Electrical Machine - I (3140913) MCQs

MCQs of Transformers

Showing 141 to 150 out of 155 Questions
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141.
A transformer has sometimes more than two ratings depending upon the use of
(a) the cooling application
(b) type of windings
(c) type of core
(d) type of insulation to be given
Answer:

Option (a)

142.
Instrument transformers are used on a.c. circuits for extending the range of
(a) ammeters
(b) voltmeters
(c) wattmeters
(d) all of the above
Answer:

Option (d)

143.
Before removing the ammeter from a current transformer, its secondary must be short circuited in order to avoid
(a) excessive heating of the core
(b) high secondary e.m.f.
(c) increase in iron losses
(d) all of the above
Answer:

Option (d)

144.
Tertiary winding in a transformer mostly
(a) Star connected
(b) Delta connected
(c) Zig-zag star connected
(d) Zig-zag delta connected
Answer:

Option (b)

145.
The main purpose of providing tertiary winding in a three-phase transformer
(a) to suppress harmonic voltages and to limit voltage unbalance when the main load is asymmetrical
(b) to interconnect three supply systems operated at different voltages
(c) to carry adding extra load to the transformer which for some reason must be kept isolated
(d) none of the above
Answer:

Option (a)

146.
Which of the following transformer insulating oil generally used in India
(a) paraffin based insulating oil
(b) naphtha based insulating oil
(c) aromatics based insulating oil
(d) olefin based insulating oil
Answer:

Option (a)

147.
The maximum allowable acidity level of power transformer insulating oil is generally taken as
(a) 1 mg of KOH/gm
(b) 0.5 mg of KOH/gm
(c) 0.3 mg of KOH/gm
(d) 2 mg of KOH/gm
Answer:

Option (c)

148.
Minimum allowable dielectric strength or break down voltage ( BDV ) of power transformer insulating oil is generally taken as
(a) 30 kV
(b) 40 kV
(c) 50 kV
(d) 20 kV
Answer:

Option (a)

149.
The maximum allowable moisture content of power transformer insulating oil is generally taken as
(a) 45 ppm
(b) 35 ppm
(c) 25 ppm
(d) 20 ppm
Answer:

Option (b)

150.
The minimum allowable flash point of power transformer insulating oil is generally taken as
(a) 140
(b) 240
(c) 40
(d) 100
Answer:

Option (a)

Showing 141 to 150 out of 155 Questions
11 12 13 14 15 16