Solved Problem on DC Motors

Submitted by tushar pramanick on Tue, 07/23/2013 - 01:38
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Q. The separately excited dc motor in the figure below has a rated armature current of 20 A and a rated armature voltage of 150 V. An ideal chopper switching at 5 kHz is used to control the armature voltage. If La= 0.1 mH, Ra= 1 , neglecting armature reaction, the duty ratio of the chopper to obtain 50% of the rated torque at the rated speed and the rated field current is

 

Options: (A) 0.4 (B) 0.5 (C) 0.6 (D) 0.7

 

Ans: D

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