[电路分析第七章.ppt

第七章 电容元件和电感元件 §7－3 动态电路的电路方程 例5、图示稳态电路，求WiL 。(1J) 6V 3Ω 8H 6Ω 6Ω Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 四. LTI电感元件的串联与并联（类似电阻） 1、并联 L 1 Lk 1 =? i(0)=?ik(0) 2、串联 等效电感 L=L1+L2+L3+ ?? Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. q=C u ?=L i i(t)=C du(t) dt u(t)=u(0)+ 1 C 0 t ? i(?)d? u(t)=L di(t) dt i(t)=i(0) + 0 t ? 1 L u(?)d? W(t)=0.5Cu2(t) W(t)=0.5Li2(t) 电流 电压 i + - u + - u i L C 元件 约束方程 电压-电流关系 连续性 储存的能量 线性时不变电容元件和电感元件主要特性汇总 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 1. 换路定律 通常，我们把电路中开关的接通、断开或电路参数的突然变化等统称为“换路”。我们研究的是换路后电路中电压或电流的变化规律，知道了电压、电流的初始值，就能掌握换路后电压、电流是从多大的初始值开始变化的。 补充：换路定律及初始值的确定 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 1 换路定律 该定律是指若电容电压、电感电流为有限值，则uC 、 iL不能跃变，即换路前后一瞬间的uC 、iL是相等的，可表达为： uC(0+)=uC(0-) iL(0+)=iL(0-) 必须注意：只有uC 、 iL受换路定律的约束而保持不变，电路中其他电压、电流都可能发生跃变。 补充：换路定律及初始值的确定 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 电路中其他变量如 iR、uR、uL、iC 的初始值不遵循换路定律的规律，它们的初始值需由t=0+电路来求得。 2. 初 始 值 的确 定 换路后瞬间电容电压、电感电流的初始值，用 uC(0+)和 iL(0+)来表示，它是利用换路前瞬间 t=0-