Transformers Archives

81. 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

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82. 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

83. In a transformer the tappings are generally provided on

primary side

secondary side

low voltage side

high voltage side

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84. 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

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85. Distribution transformers are generally designed for maximum efficiency around

90% load

Zero load

25% load

50% load

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86. 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

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

fluctuating load

poor insulation

mechanical vibrations

saturation of core

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88. Transformer breaths in when

load on it increases

load on it decreases

load remains constant

none of the above

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

Magnetostriction

Boo

Hum

Zoom

Detailed SolutionThe noise resulting

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from vibrations of laminations set by magnetic forces, is termed as

90. Material used for construction of transformer core is usually

wood

copper

aluminium

silicon steel

Detailed

Solution

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