2.相量表示式及相互关系 B E ot 0°120°240360° C E,=E∠0 120 En=E∠-120 E 120 E,=E∠120 120 EA+EB+EC=0EA  EB  EC  2. 相量表示式及相互关系 + + = 0 EA EB EC    =   =  −  =   120 120 0 E E E E E E C B A    Em B e A e C e 0°120°240°360° t 120° 120° 120°