With an armature voltage of 100V and rated field winding voltage, the speed of a separately excited DC motor driving a fan is 1000 rpm, and its armature current is 10A. The armature resistance is 1&ohm;. The load torque of the fan load i s proportional to the square of the rotor speed. Neglecting rotational losses, the value of the armature voltage (in Volt) which will reduce the rotor speed to 500 rpm is ___________.

With an armature voltage of 100V and rated field winding voltage, the

1.	With an armature voltage of 100V and rated field winding voltage, the speed of a separately excited DC motor driving a fan is 1000 rpm, and its armature current is 10A. The armature resistance is 1Ω. The load torque of the fan load i s proportional to the square of the rotor speed. Neglecting rotational losses, the value of the armature voltage (in Volt) which will reduce the rotor speed to 500 rpm is ___________.
A.	47.5
B.	37.5
C.	45
D.	21
Answer» B. 37.5

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