?_US?U+n1R2j?LR1?Un2R3?IS1?j?cR4节点法:
?Un3??U?Un1S111?1?1?(??)Un2?Un1?Un3?0R1?j?LR2R3R2R3111????j?CU???I?(??j?C)UUn3n2n1SR3R4R3例4.
Z2?I?ISZ1Z3Zo? 已知： IS?4?90A , Z1?Z2??j30 Ω Z3?30 Ω , Z?45 Ω?. 求： I解：
Z1??Z3法一：电源变换
Z2+-?(Z1//Z3)IS30(?j30)Z1//Z3??15?j15?30?j30?I ??(Z//Z)Ij4(15?j15)S13?ZI?Z1//Z3?Z2?Z15?j15?j30?455.657?45o ?o ?1.13?81.9A5?-36.9o ?Z2U0Z0+ ?I求开路电压：
??I?(Z//Z)U0S13o?U0 ?84.86?45V?ZISZ1Z3Z0?Z1//Z3?Z2??U084.86?45o?I???1.13?81.9A ?15?j45ΩZ0?Z15?j45?45 ?例5. 用叠加定理计算电流I2Z1Z2 -求等效电阻：
?IS+Z3-?I2US ?已知: US?100?45V, IS?4?0A, ?o?o Z1?Z3?50?30oΩ, Z3?50??30oΩ .(US短路):：(1) IS单独作用 ? ??ISZ3I2?ISZ2?Z3Z1Z2o50?30o' ?4?0??ooI250??30?50?30o200?30o ??2.31?30AZ3503 ??US '' I??2 ? ?Z?Z23(2) US单独作用(IS开路):o?100?45o ??1.155??135AZ1Z2
503?' ?+Z3-?I''2I2? I2? I2 ? ?' ?''US ? ?2.31?30o?1.155??135o ?(2?j1.155)?(?0.817?j0.817) ?1.183?j0.338 ?1.23??15.9oA
