E B Zn N N N,N1,N2,N3 为同电位短 接红虚线) Z zzz 一相计算电路 z1 EN,N1 ,N2 ,N3 为同电位,短 接(红虚线) 一相计算电路 EA1  EB1  EC1  A2 E'  B2 E'  C2 E'  N N1 N2 N3 A1 B1 C1 Zl1 Zl1 Zl1 A3 B3 C3 Zl 2 Zl 2 Zl 2 A4 B4 C4 Zl3 Zl3 Zl3 A2 B2 C2 ' Zi ' Zi ' Zi ' Zl ' Zl Zl Z2 Z2 Z2 + + + − − − + + + − − − EA1 A1 Z l1 A3 A4 A2 Zl 2 Zl3 1 Z ' Z2 ' Zi N N1 N2 N3 A2 E' 