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For a given compound DC machine, Net field current obtained from characteristic is equal to 7.5 A, where shunt field current is equal to 5 A, armature current is 505 A, demagnetizing current equal to 0.95 A and shunt field winding of 1000 turns at rated speed of 1000 rpm. What will be the series field turns?

For a given compound DC machine, Net field current obtained from characteristic is equal to 7.5 A, where shunt field current is equal to 5 A, armature current is 505 A, demagnetizing current equal to 0.95 A and shunt field winding of 1000 turns at rated speed of 1000 rpm. What will be the series field turns? Correct Answer 7

From the excitation balance equation, If + Ia – Ifd =If (net). 5 + 505(Nse /1000) – 0.95 = If (net). Calculating for Nse by substituting If (net), we get Nse = 6.8 that is 7 turns.

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