Page 22 - Solutions Manual to accompany Electric Machinery Fundamentals

SOLUTION By Lenz’ Law, an increasing flux in the direction shown on the core will produce a voltage that
tends to oppose the increase. This voltage will be the same polarity as the direction shown on the core, so
it will be positive. The induced voltage in the core is given by the equation
d
e  N
ind
dt
so the voltage in the windings will be
Time d e
N ind
dt
0 < t < 2 s 0.010 Wb 2.50 V
 500 t
2 s
2 < t < 5 s  0.020 Wb -3.33 V
 500 t
3 s
5 < t < 7 s 0.010 Wb 2.50 V
 500 t
2 s
7 < t < 8 s 0.010 Wb 5.00 V
 500 t
1 s

The resulting voltage is plotted below:

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