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Unformatted text preview: EE411, Final Exam, 5/12/01. Show All Work On These Pages. Name: 2‘2 Problem 1. Find the Thevenin equivalent circuit for terminals ab.
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b. Find the stored energy in the L as t —>00, and in the C as t —>00. 1500 Moo) ~  “Mym. mm. 0 /_//,,Wﬂ 1 L1 Z> 12(3 (X/D'3)('0¢‘)Z= OJbSWO 3 EE411, Final Exam, 5/12/01. Show All Work On These Pages. Name: \ Problem 3. A threephase, 60Hz, motor has internal windings connected in delta. Three
external wires, abc, connect the motor terminals to a power source. The motor operates with
the following balanced conditions:  Linetoline rms voltage = 460V
(the corresponding lineto
neutral rrns voltage is 265.6V) 0 Input P = 10kW, with power
factor = 0.90 (lagging current) External wires To
Power
Source a. Determine the rrns current magnitudes in the external abc wires that connect to the
power source. b. Determine the rms current magnitudes in the deltaconnected motor windings. Now, assume that the voltage at the motor terminals is always 460V. Three capacitors are to be connected in delta at the motor terminals to correct the net power factor to unity. What should be the MF value of each capacitor? d Determine the new rms currents in the external a—bc wires after the capacitors are added. .0 . . ~ I
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FKOM VLM I’{M"’§¢¢p ‘ MM, '9‘? EE411, Final Exam, 5/12/01. Show All Work On These Pages. Name: E E Z Problem 4. Voltage Vdc is adjustable. Find the value of vdc that causes current iO to be zero.
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 Fall '07
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