Lecture 18 - UCF Open Δ−Δ (or V−V) Connection VC =...

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Unformatted text preview: UCF Open Δ−Δ (or V−V) Connection VC = − V A − VB = −V∠ 0 o − V∠ − 120 o = V∠ + 120 o This is exactly the same voltage that would be present if the third transformer Were still there. Phase C is sometimes called a ghost phase. UCF Voltage, Current and Power in a Δ −Δ Transformer Bank Maximum power that can supply to the resistive load: PΔ − Δ = 3Vφ I φ UCF Voltage, Current and Power in a V-V Transformer Bank Maximum power that can supply to the resistive load: PV −V = Vφ I φ cos( 0 o − ( − 30 o )) + Vφ I φ cos( − 120 o − ( − 90 o )) = Vφ I φ cos 30 o + Vφ I φ cos( − 30 o ) = 3Vφ I φ (from transformer) 3 /3 = 0 . 866 2/3 or PV − V = 3V φ Iφ 3 = 3V φ I φ ⇒ (from balanced 3-phase load) 3 phase PV − V 3 = = 0 . 577 3 PΔ − Δ UCF Reactive Power of V-V Transformers 3 Reactive power of transformer 1: 1 QTrans 1 = Vφ I φ sin( 0 − ( − 30 )) = Vφ I φ sin 30 = Vφ I φ 2 Reactive po er Reacti e power of transformer 2: o o o 1 QTrans 2 = Vφ I φ sin( − 120 o − ( − 90 o )) = Vφ I φ sin( − 30 o ) = − Vφ I φ 2 UCF Open Y − Open Δ Connection p p Note the presence of neutral lead at the primary side. UCF Scott T Connection (3 Phase to 2 Phase) ( ) 3 = 0 . 866 2 UCF 3 Phase Scott T Connection UCF Magnetizing Current g g N P i P − N S i S = H ( B )l C = F NS iS ) N P i P − N S i S = N P (i P − NP NS Define : iM = iP − iS NP N P iM = H ( φ Ac )lC = F(φ ) UCF Effects of Peak Flux on Magnetizing Current g g Saturated! I M ,rms 1 T 2 = ∫0 iM (t )dt T UCF Maximum Voltage g Steady State v P (t ) = 2V cos( ω t ) = N P d φ y ( dt 1 φ= NP ∫v P (t ) dt = 2V P , rms ωN P sin( ω t ) φ max = 2V P , rms 2πfN P 2πfN Pφ max ≈ 4 .44 fN P Bmax Ac 2πfN Pφ max ≈ 4 .44 fN S Bmax Ac V P , rms , max = V S , rms , max = UCF Voltage and Frequency Ratings g q y g Volt-Second Balance Vrms,max = 2πfNφmax ≈ 4.44 fNBmax Ac or : Vrms,max f = 2πNφmax ≈ 4.44NBmax Ac ...
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This document was uploaded on 11/03/2009.

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Lecture 18 - UCF Open Δ−Δ (or V−V) Connection VC =...

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