Exam5-Spring08 - EEL 3211 Test 5 May 1, 2008 Time limit: 50...

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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 no-load 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 25-kW, 125-V 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 open-circuit armature voltage is 125 V. The armature resistance is 0.02 . 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.

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