△Y变换的等效条件: i1Y|1 1△ R 12△ L31△ R u 12Y 12 31 31Y 3△+ 、3Y+ 2 R 23 3 2 23Y 23△ 等效的条件:1△=i1y12△=W12Y l2△=Z2Y 23△ 23Y △3Y l31△=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△ +4n1 L12△ 12 31△ R 12 31 12Y 31Y R2 3 34+ 22Y Y+ 23 23 2 23△ 23Y △接:用电压表示电流 Y接:用电流表示电压 1△=12-31÷12△231△ 12y rir -r2i2y 12 31 si23-42、u2△-212△ H23Y=R2i2r-R3i3r (2) R23R1 12 Ir +i2y +ljr=0 3 23△ 3△-431123 R 31 R 23
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