Transformers

31. The degree of mechanical vibrations produced by the laminations of a transformer depends on

tightness of clamping
gauge of laminations
size of laminations
all of the above

Detailed SolutionThe degree of mechanical vibrations produced by the laminations of a transformer depends on

32. If R2 is the resistance of secondary winding of the transformer and K is the transformation ratio then the equivalent secondary resistance referred to primary will be

$$ rac{{{{ ext{R}}_2}}}{{sqrt { ext{K}} }}$$
$$ rac{{{{ ext{R}}_2}}}{{{{ ext{K}}^2}}}$$
$$ rac{{{ ext{R}}_2^2}}{{{{ ext{K}}^2}}}$$
$$ rac{{{ ext{R}}_2^2}}{{ ext{K}}}$$

Detailed SolutionIf R2 is the resistance of secondary winding of the transformer and K is the transformation ratio then the equivalent secondary resistance referred to primary will be

33. In a transformer the tappings are generally provided on

primary side
secondary side
low voltage side
high voltage side

Detailed SolutionIn a transformer the tappings are generally provided on

34. The function of breather in a transformer is

to provide oxygen inside the tank
to cool the coils during reduced load
to cool the transformer oil
to arrest flow of moisture when outside air enters the transformer

Detailed SolutionThe function of breather in a transformer is

35. Distribution transformers are generally designed for maximum efficiency around

90% load
Zero load
25% load
50% load

Detailed SolutionDistribution transformers are generally designed for maximum efficiency around

36. The permissible flux density in case of cold rolled grain oriented steel is around

1.7 Wb/m2
2.7 Wb/m2
3.7 Wb/m2
4.7 Wb/m2

Detailed SolutionThe permissible flux density in case of cold rolled grain oriented steel is around

37. The main reason for generation of harmonics in a transformer could be

fluctuating load
poor insulation
mechanical vibrations
saturation of core

Detailed SolutionThe main reason for generation of harmonics in a transformer could be

38. Transformer breaths in when

load on it increases
load on it decreases
load remains constant
none of the above

Detailed SolutionTransformer breaths in when

39. The noise resulting from vibrations of laminations set by magnetic forces, is termed as

Magnetostriction
Boo
Hum
Zoom

Detailed SolutionThe noise resulting from vibrations of laminations set by magnetic forces, is termed as

40. Material used for construction of transformer core is usually

wood
copper
aluminium
silicon steel

Detailed SolutionMaterial used for construction of transformer core is usually

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