二、△一Y变换的等效条件 U31△ U12△ 31Y R W12Y 3 R23 2 W23△ 等效的条件：i1a=i1y,2A=i2y,△=Y, 且 W12A=U12Y,U23A =U23Y,U31A=U31YR31 R12 R23 i2 ' i3' i1' 1 3 2 — _ _ + + + u31' u23' u12' R1 R3 R2 i1Y i3Y i2Y 1 3 2 — — + — + + u31Y u23Y u12Y ㅹ᭸ⲴᶑԦ: i1' =i1Y , i2 ' =i2Y , i3 ' =i3Y , ф u12' =u12Y , u23' =u23Y , u31' =u31Y Ҽǃ'—Y ਈᦒⲴㅹ᭸ᶑԦ