电工技术 换路定则的.ppt

3.2.1 换路定理 换路: 电路状态的改变。如： §3.2储能元件和换路定则 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 换路定理: 在换路瞬间，电容上的电压、电感中的电流不能突变。 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 换路瞬间，电容上的电压、电感中的电流不能突变的原因解释如下： 自然界物体所具有的能量不能突变，能量的积累或 释放需要一定的时间。所以 * Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. * 所以电容电压 不能突变 从电路关系分析 K 闭合后，列回路电压方程： Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 3.2.2 初始值的确定 求解要点：换路定理 初始值（起始值）：电路中 u、i 在 t=0+ 时 的大小。 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 例1： 在t=0+时，电容相当于短路 在t=时，电容相当于断路 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 例2： U=12V R1=2k R2=4k C=1F 在t=0+时，电容相当于一个恒压源 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 例3 R L Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 已知: 电压表内阻 设开关 K 在 t = 0 时打开。 求: K打开的瞬间,电压表两端的电压。 例4 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 注意:实际使用中要加保护措施 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 小结 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.