Questions
41
Delta/star transformer works satisfactorily when
Answer: on balanced as well as unbalanced loads
42
Star/star transformers work satisfactorily when
Answer: load is balanced only
43
Which of the following property is not necessarily desirable in the material for transformer core ?
Answer: High thermal conductivity
44
Distribution transformers are generally designed for maximum efficiency around
Answer: 50% load
45
The main reason for generation of harmonics in a transformer could be
Answer: saturation of core
46
Gas is usually not liberated due to dissociation of transformer oil unless the oil temperature exceeds
Answer: 150°C
49
In a transformer the resistance between its primary and secondary is
Answer: infinite
50
The highest voltage for transmitting electrical power in India is
Answer: 400 kV
51
The function of conservator in a transformer is
Answer: to take care of the expansion and contraction of transformer oil due to variation of temperature of sur-roundings
52
The thickness of laminations used in a transformer is usually
Answer: 0.4 mm to 0.5 mm
53
Material used for construction of transformer core is usually
Answer: silicon steel
54
Hysteresis loss in a transformer varies as CBmax = maximum flux density)
Answer: Bmax1-6
55
The noise resulting from vibrations of laminations set by magnetic forces, is termed as
Answer: hum
58
The chemical used in breather for transformer should have the quality of
Answer: absorbing moisture
59
The use of higher flux density in the transformer design
Answer: reduces weight per kVA
60
Buchholz’s relay gives warning and protection against
Answer: electrical fault inside the transformer itself
