△Y变换的等效条件: 1△ L12△ L31△ R R 12Y 12 31 31Y R 3 Δ+ Y Y+ 23 2 23Y L 23△ 等效的条件:i1△=i1Y l12△=l12Y l2△=l2Y 23△ L 23Y △ Y 31△=l31Y
R12 R31 R23 i3 i2 i1 1 2 3 + + + – – – u12 u23 u31 R1 R2 R3 i1Y i2Y i3Y 1 2 3 + + – + – – u12Y u23Y u31Y i1 = i1Y i2 = i2Y i3 = i3Y —Y 变换的等效条件: u12 = u12Y u23 = u23Y u31 = u31Y 等效的条件：
1△ u 12△ 31△ R R R 1 12 31 ury U31Y R 3 3△ 3Y+ 223R 23 3 2 L 23△ 23Y △接:用电压表示电流 Y接:用电流表示电压 2△ 31△ △=l12-l31= R R u12y= rily -r2i2y 12 i2△=23-i12=223212△ 23y=R2i2y-R3y(2) R23R12 1) i1r +i2r +i3y=0 3△=l31一 1△ 23=31 L23△ 31 R
接: 用电压表示电流 Y接: 用电流表示电压 R12 R31 R23 i3 i2 i1 1 2 3 + + + – – – u12 u23 u31 R1 R2 R3 i1Y i2Y i3Y 1 2 3 + + – + – – u12Y u23Y u31Y (1) (2) i12 i23 i31 1 12 31 i = i − i 31 31 12 12 R u R u = − 2 23 12 i = i − i 12 12 23 23 R u R u = − 3 31 23 i = i − i 23 23 31 31 R u R u = − Y Y Y u R i R i 12 = 1 1 − 2 2 Y Y Y u R i R i 23 = 2 2 − 3 3 i 1Y + i 2Y + i 3Y = 0