SSE JE Electrical Engineering 10 Dec 2020 Papers

Question : 156 of 200

Marks: +1, -0

An alternator on open-circuit generates 360 V at 60 Hz when the field current is 3.6 A. Neglecting saturation, determine the open-circuit EMF when the frequency is 40 Hz and the field current is 2.4 A.

110 V
140 V
210 V
160 V

Validate

Solution:

\E _{1}=360 \V , \I _{ \f 1}=3.6 \A , \f _{1}=60 \Hz

\I _{ \f 2}=2.4 \A , \f _{2}=40 \Hz

∴\E _{2}=( \E _{1} \I _{ \f 2} \f _{2}) /( \I _{ \f 1} \f _{1})

=(360 × 40 × 2.4) /(3.6 ×60)

=160 \V

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