例 E B马 2922 其中 ∠-30°E E E Zn a Z E NN..N C 为同电位短 接(红虚线) 2动z1z22乙例 EA1  EB1  EC1  EA2  EB2  EC2  Z2 Z2 Z2 Zl Zl Zl Zl3 Zl3 Zl3 Zl 2 Zl 2 Zl 2 Zl1 Zl1 Zl1 Zi Zi Zi B3 C3 A2 B2 C2 A4 B4 C4 A1 A3 B1 C1 − + + − + − − + + + − 其中 − ' 2 2 1 30 3 E E A A =  − ' 1 3 Z Z i i = ' 1 1 1 3 Z Z = N,N1 ,N2 ,N3 为同电位,短 接(红虚线) 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 + + + − − − + + + − − −