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Midterm2_2006_Term1

# Midterm2_2006_Term1 - ENG2MM3 Mid-Term Exam#2 Term 2...

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ENG2MM3 Mid-Term Exam. #2, Term 2, 2006~2007 2 pages 11:30am ~ 12:20pm, Nov. 20, 2006 page 1 of 2 There are 3 Questions in Total (2 Pages) Q.1: A 316-V three-phase power system is shown below. It consists of an ideal 316-V Δ -connected three- phase generator connected through a three-phase transmission line to a Δ− connected load. The transmission line has an impedance of 0.16+ j 0.18 Ω per phase, and the load has an impedance of 20+ j 24 Ω per phase. For this simple power system, find (a) the line current I L and the phase current I Φ ; (b) the load’s line and phase voltages V Φ_ LL and V Φ_ L ; and (c) the real, reactive and apparent powers consumed by the load. Q.2: (20 points) A step-down transformer is rated 120 kVA, 12.79KV-240V. Open-circuit and short- circuit tests were conducted with the following results. Determine the equivalent circuit parameters of the transformer referred to the high side. V oc = 120 V V sc = 250 V I oc = 24 A I sc = 25 A P oc = 1000 W P sc = 1200 W Fig. 1: The three-phase circuit for Q2 V φ = 316 V V φ V φ V φ 0.16 Ω j 0.18 Ω 0.16 Ω j 0.18 Ω 0.16 Ω j 0.18

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