Exam2_04_SP2011 Solution

# Exam2_04_SP2011 Solution - I ph I Line 3300 V 5716V 606 A...

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ELECTRICAL ENGINEERING DEPARTMENT California Polytechnic State University EE 255-04 EXAM #2 May 25, 2011 I have neither given nor received unauthorized assistance during this test. Name (Print)_______________________________ Signature:__________________________ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Problem 1 (10 Points) Three single-phase transformers each rated 2000-KVA, 33,000:3,300-V, and 60-Hz are connected in wye-delat configuration. The three-phase transformer is supplying a three- phase rated load of 6000 KVA at 3300 V line-to-neutral and unity power factor. Determine the magnitudes of the LVS and HVS line and phase voltages and line and phase currents. Assume ideal transformers. Solution: LVS Y-Connected A I L A I V V V V ph Line ph Line ph 606 606 3 3 3 2000 3 5716 3300 3 3300 = = = = = = = . * * * HVS Delta-Connected A L A I V V V Line ph Line ph 105 6 60 3 6 60 33 3 2000 3 33000 = = = = = = = . * . * * Low Voltgae Side (LVS) Y High Voltgae Side (HVS) Δ V ph V Line I ph I Line V ph V Line

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Unformatted text preview: I ph I Line 3300 V 5716V 606 A 606A 33000 V 33000 V 60.6 A 105 A Problem 2 (15 Points) A 208-V, four-pole, 60-Hz, Y-connected three-phase induction motor has the following parameters: Ω = Ω = 43 22 1 1 . . X R Ω = Ω = 43 127 2 2 . . X R 1 a 15 = Ω = m X Determine: (1) Slip at max. T (2) Maximum Torque (3) R ext that will make T st =T max . 14.5% 100 N-m 0.749Ω Solution Ω + = + = Ω ° ∠ = + + = 421 . 208 . 7 . 63 469 . 43 . 15 22 . ) 43 . 22 . ( 15 j jX R Z j j j Z Th Th Th Th % 5 . 14 100 * ) 43 . 421 . ( ) 208 . ( 127 . 2 2 . = + + = T Max S V j j V Th ° ∠ = + ° ∠ = 8 . 7 . 116 43 . 15 22 . 15 * 120 m N T Max-= + + + = 100 ] ) 43 . 421 . ( ) 208 . ( 208 . [ * 2 377 ) 7 . 116 ( 5 . 1 2 2 2 . Ω = + + + = = 749 . ) 43 . 421 . ( ) 208 . ( 127 . 1 2 2 . ext ext T Max R R S...
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## This note was uploaded on 12/19/2011 for the course EE 295 taught by Professor Alishaban during the Fall '11 term at Cal Poly.

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Exam2_04_SP2011 Solution - I ph I Line 3300 V 5716V 606 A...

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