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solex1f11

# solex1f11 - ECE473 EXAM#1 SOLUTIONS FALL 2011 Instructions...

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ECE473 EXAM #1 – SOLUTIONS FALL 2011 Instructions : 1. Closed-book, closed-notes, open-mind exam. 2. Work each problem on the exam booklet in the space provided. 3. Write neatly and clearly for partial credit. Cross out any material you do not want graded. Name : Problem 1 : /20 Problem 2 : /30 Problem 3 : /20 Problem 4 : /30 Total : /100 Single-Phase AC Circuits : ˜ V = ¯ Z ˜ I = | ˜ V || ˜ I | ̸ ϕ, ϕ = θ v - θ i ¯ S = P + jQ = ˜ V ˜ I = | ˜ V || ˜ I | ̸ ϕ = ¯ Z | ˜ I | 2 = | ˜ V | 2 ¯ Z S = P 2 + Q 2 = V I = ZI 2 = V 2 Z P = V I cos ϕ = RI 2 = V 2 R Q = V I sin ϕ = XI 2 = V 2 X Three-Phase AC Circuits : ¯ Z = 3 ¯ Z Y S 3 ph = 3 V LN I L = 3 V LL I L P 3 ph = 3 V LN I L cos ϕ = 3 V LL I L cos ϕ Q 3 ph = 3 V LN I L sin ϕ = 3 V LL I L sin ϕ ˜ V AB = ( 3 ̸ 30 o ) ˜ V AN , ˜ V BC = ( 3 ̸ 30 o ) ˜ V BN , ˜ V CA = ( 3 ̸ 30 o ) ˜ V CN ˜ I aA = ( 3 ̸ - 30 o ) ˜ I AB , ˜ I bB = ( 3 ̸ - 30 o ) ˜ I BC , ˜ I cC = ( 3 ̸ - 30 o ) ˜ I CA 1

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Problem 1 (20 Points) 15 10 j8 6 j8 + - + - + - j2.88 3.84 I ~ V ~ I ~ V ~ I ~ V ~ Find the line current magnitude I = | ˜ I |
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solex1f11 - ECE473 EXAM#1 SOLUTIONS FALL 2011 Instructions...

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