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EEL 3211
Test 5
May 1, 2008
Time limit: 50 minutes, Closed note, closed book, one (1) 8½ x 11 sheet of notes allowed.
1. A separately excited DC motor is shown below. The field current and terminal voltage
V
T
are assumed
constant.
a.
(10%) Assuming that the motor is initially stationary. If the switch closes at t = 0, describe in words,
clearly and briefly, using equations to support you explanation, how the motor achieves its steady state
speed under noload conditions. Neglect all losses and armature reaction. Be sure to specify the behavior
of armature current
I
A
and motional emf
E
A
in your description.
Brevity, clarity, and neatness count!
b.
(5%) How would you answer change if armature reaction were included?
2. A 25kW, 125V separately excited DC machine (like the one above) is operated at a constant speed of 3000
rev/min with a constant field current such that the opencircuit armature voltage is 125 V. The armature
resistance is 0.02
Ω
. If the terminal voltage is 128 V compute:
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This note was uploaded on 07/28/2011 for the course EEL 3211 taught by Professor Staff during the Summer '08 term at University of Florida.
 Summer '08
 Staff
 Volt

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