方法二:戴维南等效变换 求开路电压: (Z1∥23) 84.86∠45°V 求等效电阻: 2s=Z1∥23+Z 15-j4≤2 q 84.86∠45 15-145+45 =1.13∠81.9°A方法二：戴维南等效变换 84.86 45 V ( // ) o 0 1 3 =  U = I  S Z Z Zeq Z 0 • U • I + - Z2 S I  Z1 Z3 U0  求开路电压： 求等效电阻： 15 j45Ω // 1 3 2 = − Zeq = Z Z + Z 1.13 81.9 A 15 45 45 84.86 45 o 0 0 =  − +  = + = Z Z j U I   