SSE JE Electrical Engineering 24 March 2021 Shift 2 Paper

Question : 179 of 200

Marks: +1, -0

The field coils of a 6-pole DC generator each having 500 turns are connected in series. When the field is excited, there is a magnetic flux of 0.02 Wb/pole. If the field circuit is opened in 0.02 s and the residual magnetism is 0.002 Wb/pole, calculate the average voltage induced across the field terminals.

16200 V
18000 V
14300 V
3000 V

Validate

Solution:

P = Number of poles = 6
N = Total turns = 6 × 500 = 3000 (since 500 turns per pole in series)
Total initial flux = 6 × 0.02 = 0.12 Wb. (since number of poles is 6)
Total residual flux = 6 × 0.002 = 0.012 Wb
Change in flux, dϕ = 0.12 - 0.012 = 0.108 Wb
Time of opening of circuit, dt = 0.02 second
From concept,
Induced EMF (E)

=3000 × {0.108}/{0.02}= 1 6 , 2 0 0 \V

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