Page 209 - Solutions Manual to accompany Electric Machinery Fundamentals

SOLUTION
(a) If the speed of rotation  of the shaft is 500 rad/s, then the voltage induced in the rotating loop will
be
e ind  2rlB


e ind   2 0.25 m 0.5 m 0.4 T 500 rad/s  50 V
Since the external battery voltage is only 48 V, this machine is operating as a generator, charging the
battery.
(b) The current flowing out of the machine is approximately

e  V  50 V 48 V  
i  ind B     5.0 A
R  0.4  
(Note that this value is the current flowing while the loop is under the pole faces. When the loop goes
beyond the pole faces, e will momentarily fall to 0 V, and the current flow will momentarily reverse.
ind
Therefore, the average current flow over a complete cycle will be somewhat less than 5.0 A.)
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