R R,2 +in+i,=0 RR2+R,R,+r,R rR2I+r,R3+r3R 31 对于Y: u,,=R,, - R,i, i R R.R+rr+Rr RR, |+RR,+r,R R u23=R, L, -Ri313-RR,+RR,+R,R,31 RR2+Km/ tigi 3 因为1=计所以系数相等 R →Rn=RR2+R2R3+R3R RRR+rr+R. R i1=12-131 R R,R+R.r,+R.r =u12/R12-u31/R3r R23 RR2+R,R,+Rir R R RR+r.+rr rbi rir2+r,R,+r,r R Y形连接→Δ连接公式 将上述三式相加并右边通分R,+Rn+R1=(R2+RR:+RR) RRR R1R2+R2R3+R3R1=R2R3=R31R2代入上式求→R同理可求R2R3 RR RR R.R R R R rtr+r R,+R,,+R rtr+r 12 23 31 31 23 3 12 23 31 23 12 2 12 23 31 12 31 1 1 2 2 3 3 1 12 3 31 2 1 2 3 31 31 1 23 23 12 23 1 2 2 3 3 1 1 23 2 2 3 3 31 12 1 2 2 3 3 1 3 12 1 1 2 2 23 31 1 2 2 3 3 1 2 1 2 3 12 1 1 1 0 R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R Y R R R R R R u R R | R R R R R u R i R i u u R R | R R R R R u R i R i u u R R | R R R R R i i i u + + = + + = + + = + + = = → + + + + = →   + + → = + + = + + → = + + = + + → = + + = =  + + − + + = − = + + − + + = − = + + − + + + + = = R R R (R R R R R R ) R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R i i R R R R R R R i R R R R R R R i R R R R R R R i 1 2 3 2 1 2 2 3 3 1 12 23 31 2 1 2 2 3 3 1 1 2 2 3 3 1 2 1 2 2 3 3 1 1 2 2 3 3 1 1 3 1 2 2 3 3 1 1 2 2 3 3 1 3 12 1 1 1 2 2 3 3 1 2 3 1 2 2 3 3 1 1 2 1 2 2 3 3 1 3 1 代入上式求 同理可求 将上述三式相加并右边通 分 形连接 连接公式 因 为 所以系数相等  对于Y： =i12-i31 =u12/R12-u31/R31 1 i