电工学第六版课后答案秦曾煌.ppt

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1、暂态过程初始值的确定1．解：(1)由换路前电路求由已知条件知根据换路定则得：已知：换路前电路处稳态，C、L均未储能。试求：电路中各电压和电流的初始值。CR2S(a)UR1t=0+-LEvaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.暂态过程初始值的确定2:,换路瞬间，电容元件可视为短路。,换路瞬间，电感元件可视为开路。iC、uL产生突变(2)由t=0+电路，求其余各电流、电压的初始值CR2S(a)UR1

2、t=0+-LiL(0+)UiC(0+)uC(0+)uL(0+)_u2(0+)u1(0+)i1(0+)R2R1+++__+-(b)t=0+等效电路Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.3-1：换路前电路处于稳态。试求图示电路中各个电压和电流的初始值。解：(1)由t=0-电路求uC(0–)、iL(0–)换路前电路已处于稳态：电容元件视为开路；电感元件视为短路。由t=0-电路可求得：2+_RR2R

3、1U8Vt=0++4i14iC_uC_uLiLR3442+_RR2R1U8V++4i14iC_uC_uLiLR3LCt=0-等效电路Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.3-2：换路前电路处于稳态。试求图示电路中各个电压和电流的初始值。解：由换路定则：2+_RR2R1U8Vt=0++4i14iC_uC_uLiLR3442+_RR2R1U8V++4i14iC_uC_

4、uLiLR3LCt=0-等效电路Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.3-3：换路前电路处稳态。试求图示电路中各个电压和电流的初始值。解：(2)由t=0+电路求iC(0+)、uL(0+)由图可列出带入数据t=0+时等效电路4V1A42+_RR2R1U8V+4iC_iLR3iiL(0+)uc(0+)2+_RR2R1U8Vt=0++4i14iC_uC_uLiLR34Evaluatio

5、nonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.3-4：换路前电路处稳态。试求图示电路中各个电压和电流的初始值。解：解之得并可求出2+_RR2R1U8Vt=0++4i14iC_uC_uLiLR34t=0+时等效电路4V1A42+_RR2R1U8V+4iC_iLR3iEvaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Co

6、pyright2004-2011AsposePtyLtd.计算结果：电量换路瞬间，不能跃变，但可以跃变。2+_RR2R1U8Vt=0++4i14iC_uC_uLiLR34Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.结论1.换路瞬间，uC、iL不能跃变,但其它电量均可以跃变。3.换路前,若uC(0-)0,换路瞬间(t=0+等效电路中),电容元件可用一理想电压源替代,其电压为uc(0+);换路

7、前,若iL(0-)0,在t=0+等效电路中,电感元件可用一理想电流源替代，其电流为iL(0+)。2.换路前,若储能元件没有储能,换路瞬间(t=0+的等效电路中)，可视电容元件短路，电感元件开路。Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.4：用三要素法求解解：电路如图，t=0时合上开关S，合S前电路已处于稳态。试求电容电压和电流、。(1)确定初始值由t=0-电路可求得由换路定则t=0-等效电路9m

8、A+-6kRS9mA6k2F3kt=0+-CREvaluationonl