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1、7.3 Y形起電力+不平衡Y形負荷7.3 Y-Connected Power Supplies + Unbalanced Y-Connected Loads 要点三相Y形方式一般的計算General calculation of Y-connected three phase system教科書該当p7.2.1 (b) Y起電力回路、不平衡Y結線負荷 p.156Y形不平衡負荷回路 p.156p線路電流求、図描Calculate line current and draw vector diagramp 条件P非対称三相起電力 Asymmetric three phase power suppl
2、yEa = |E|, Eb a2|E|, Ec a|E|P不平衡負荷 Unbalanced loadsZa Zb Zcp N-N間電圧EnP各Z流電流EnEa - En = Za IaEb - En = Zb IbEc - En = Zc Ic- En = Zn IN (7.6) Ia = = (Ea - En)YaEa - EnZaIb = = (Eb - En)YbEb - EnZbIc = = (Ec - En)YcEc - EnZcIN = = - En YN (7.7)- EnZNEnP 、N電流総和 0 l Ia + Ib + Ic + IN = 0l (Ea - En)Ya +
3、(Eb - En)Yb + (Ec - En)Yc - En YN = 0l En (Ya + Yb + Yc + YN) = EaYa + EbYb + EcYc En = (7.9)EaYa + EbYb + EcYcYa + Yb + Yc + YN非対称起電力不平衡負荷非対称起電力不平衡負荷式式 (7.7), (7.9)(7.7), (7.9) 計算計算対称平衡対称平衡使一般式使一般式中性線YN = 0 , IN = 0p 図 Vector diagram起電力描通常Ea基準中性点間電圧 En 描原点 N 点相当Z 加電圧 Ea=Ea-En Ea=En+Ea Eb=Eb-En Eb=E
4、n+Eb Ec=Ec-En Ec=En+Ec 線路電流描 Ia = = = -ja EaZaEa|Za| jaEa|Za| IaEaja遅大|Ea|Za| Ea対描 En 始点Ib , Ic 同様例題 Example p.157 非対称Y形起電力、不平衡Y形負荷三相交流回路、各線電流求。 Calculate each line current of the three phase circuit with asymmetrical Y-type power supply and unbalanced loads.P YN = 0、Eq. (7.9), (7.9)使中性点間電圧 En En =E
5、aYa + EbYb + EcYcYa + Yb + Yc=120(0.5- j 0.4)+(- 60- j 80)(0.3- j 0.2)+(- 60+ j 80)(0.4+ j 0.3)(0.5- j 0.4)+(0.3- j 0.2)+(0.4+ j 0.3)= - 8.24- j 40.4 = 41.23 - 101.3 (V)線路電流 Ia = (Ea - En)Ya = 120 - (- 8.24- j 40.4)(0.5- j 0.4) = 80.3 - j 31.1 = 86.1 - 21.2 (A) Ib = (Eb - En)Yb = - 23.5 - j 1.5 = 23.5 - 176.4 (A) Ic = (Ec - En)Yc = - 56.8 + j 32.6 = 65.5 150.2 (A)図 演習 Exercise 例題、不平衡負荷値図変場合各線路電流求、図描。 In the previous example, the value of loads was changed as shown in the figure. Calculate each line current and draw vector diagram.
