1Y-△等效变换 R n 2 R △一Y 23 Y-△ R,R R12=R1+R,+ R R12R31 R R12+R23+R31 RaR R R+R2+ RR R 31-12 R R 12 +R22+R R21=R2+R1+ R3R RaR R R R12+R23+R31Y- 2 3 1 3 1 3 1 1 2 3 2 3 2 3 3 1 2 1 2 1 2 R R R R R R R R R R R R R R R R R R = + + = + + = + + 1 2 2 3 3 1 2 3 3 1 3 1 2 2 3 3 1 2 3 1 2 2 1 2 2 3 3 1 1 2 3 1 1 R R R R R R R R R R R R R R R R R R + + = + + = + + = -Y Y- 等效变换 U12 U12 R2 1 2 3 R3 R1 R12 R23 R31 1 2 3