Y形起电力不平衡Y形负荷.ppt

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1、7.3Y形起電力+不平衡Y形負荷7.3 Y-Connected Power Supplies+Unbalanced7.3 Y-Connected Power Supplies+Unbalanced Y-Connected Loads Y-Connected Loads 要点p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.156p線路電流求、図描Calculate line current and draw vect

2、or diagramp条件P非対称三相起電力 Asymmetric three phase power supply Ea=|E|,Eb a2|E|,Ec a|E|P不平衡負荷 Unbalanced loads Za Zb Zcpp N N-N N 間電圧間電圧E En nP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)-EnZNEnPP 、N N 電流総和電流総和 0 0 l I

3、a+Ib +Ic +IN=0l(Ea-En)Ya+(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=0pp 図図 Vector diagramVector 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=En+Eb

4、Ec=Ec-En Ec=En+Ec 線路電流描線路電流描 Ia=-j ja EaZaEa|Za|j jaEa|Za|IaEaj ja遅大|Ea|Za|Ea対描En始点Ib,Ic 同様例題ExampleExamplep.157p.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EnEn=EaYa+E

5、bYb+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ExerciseExercise 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.