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--- electrical_engineering_1:introduction_in_alternating_current_technology [2023/12/15 23:10]
mexleadmin [Bearbeiten - Panel]
+++ electrical_engineering_1:introduction_in_alternating_current_technology [2023/12/20 09:53]
mexleadmin
@@ Zeile 824: / Zeile 824: @@
 <panel type="info" title="Exercise 6.5.5 Complex Calculation I"> <WRAP group><WRAP column 2%>{{fa>pencil?32}}</WRAP><WRAP column 92%>
-The following two currents with similar frequencies, but different phases have to be added. Use complex calulation!
+The following two currents with similar frequencies, but different phases have to be added. Use complex calculation!
   * $i_1(t) = \sqrt{2} \cdot 2 ~A \cdot \cos (\omega t + 20°)$
   * $i_2(t) = \sqrt{2} \cdot 5 ~A \cdot \cos (\omega t + 110°)$
@@ Zeile 836: / Zeile 836: @@
 What are the values for $\underline{Z}_1$ and $\underline{Z}_2$?
+#@HiddenBegin_HTML~656Sol,Solution~@#
+It's a good start to write down all definitions of the given values:
+  * the given values for the series circuit ($\square_\rm s$) and the parallel circuit ($\square_\rm p$) are: \begin{align*} R_\rm s = 60 ~\Omega , \quad X_\rm s = 0 ~\Omega \\ R_\rm p = 25 ~\Omega , \quad X_\rm p = 0 ~\Omega \\ \end{align*}
+  * the series circuit and the parallel circuit results into: \begin{align*}  R_{\rm s} = \underline{Z}_1 + \underline{Z}_2 \tag{1} \\ R_{\rm p} = \underline{Z}_1 || \underline{Z}_2  \tag{2} \\ \end{align*}
+  * the unknown values of the two impedances are: \begin{align*} \underline{Z}_1 = R_1 + {\rm j}\cdot X_1  \tag{3} \\ \underline{Z}_2 = R_2 + {\rm j}\cdot X_2 \tag{4} \\ \end{align*}
+Based on $(1)$,$(3)$ and $(4)$:
+\begin{align*}
+R_\rm s         &= \underline{Z}_1     &&+ \underline{Z}_2  \\
+                &= R_1 + {\rm j}\cdot X_1    &&+ R_2 + {\rm j}\cdot X_2  \\
+\rightarrow 0   &= R_1 + R_2 - R_\rm s &&+ {\rm j}\cdot (X_1 + X_2)  \\
+\end{align*}
+Real value and imaginary value must be zero:
+\begin{align*}
+R_1 &= R_{\rm s} - R_2  \tag{5} \\
+X_1 &= - X_2  \tag{6}
+\end{align*}
+Based on $(2)$ with $R_\rm s = \underline{Z}_1 + \underline{Z}_2$  $(1)$:
+\begin{align*}
+R_{\rm p}                  &= {{\underline{Z}_1 \cdot \underline{Z}_2}\over{\underline{Z}_1 + \underline{Z}_2}} \\
+                           &= {{\underline{Z}_1 \cdot \underline{Z}_2}\over{R_\rm s}} \\ \\
+R_{\rm p} \cdot R_{\rm s}  &=   \underline{Z}_1 \cdot \underline{Z}_2 \\
+                           &= (R_1 + {\rm j}\cdot X_1)\cdot (R_2 + {\rm j}\cdot X_2)     \\
+                           &= R_1 R_2 + {\rm j}\cdot (R_1 X_2 + R_2 X_1) - X_1 X_2     \\
+\end{align*}
+Substituting $R_1$ and $X_1$ based on $(5)$ and $(6)$:
+\begin{align*}
+R_{\rm p} \cdot R_{\rm s}  &=  (R_{\rm s} - R_2 )  R_2 + {\rm j}\cdot ((R_{\rm s} - R_2 )  X_2 - R_2 X_2) + X_2 X_2     \\
+\rightarrow 0 &=  R_{\rm s} R_2 - R_2^2  + X_2^2 - R_{\rm p} \cdot R_{\rm s}  + {\rm j}\cdot ((R_{\rm s} - R_2 )  X_2 - R_2 X_2)      \\
+\end{align*}
+Again real value and imaginary value must be zero:
+\begin{align*}
+&=  j\cdot ((R_{\rm s} - R_2 )  X_2 - R_2 X_2)     \\
+  &=           R_{\rm s}X_2 - 2 \cdot R_2 X_2        \\
+\rightarrow    R_2 = {{1}\over{2}} R_{\rm s} \tag{7} \\ \\
+&= R_{\rm s} R_2 - R_2^2  + X_2^2 - R_{\rm p} \cdot R_{\rm s}  \\
+  &= R_{\rm s} ({{1}\over{2}} R_{\rm s}) - ({{1}\over{2}} R_{\rm s})^2  - X_2^2 - R_{\rm p} \cdot R_{\rm s}  \\
+  &= {{1}\over{4}} R_{\rm s}^2 + X_2^2 - R_{\rm p} \cdot R_{\rm s}  \\
+\rightarrow    X_2 = \pm \sqrt{R_{\rm p} \cdot R_{\rm s}  - {{1}\over{4}} R_{\rm s}^2 } \tag{8} \\ \\
+\end{align*}
+The concluding result is:
+\begin{align*}
+(5)+(7): \quad R_1 &= {{1}\over{2}} R_{\rm s} \\
+(7): \quad R_2 &= {{1}\over{2}} R_{\rm s} \\
+(6)+(8)  \quad X_1 &= \mp \sqrt{R_{\rm p} \cdot R_{\rm s}  - {{1}\over{4}} R_{\rm s}^2 } \\
+(8): \quad X_2 &= \pm \sqrt{R_{\rm p} \cdot R_{\rm s}  - {{1}\over{4}} R_{\rm s}^2 }
+\end{align*}
+#@HiddenEnd_HTML~656Sol,Solution ~@#
+#@HiddenBegin_HTML~656Res,Result~@#
+\begin{align*}
+R_1 &= 30~\Omega \\
+R_2 &= 30~\Omega \\
+X_1 &= \mp \sqrt{600}~\Omega \approx \mp 24.5~\Omega \\
+X_2 &= \pm \sqrt{600}~\Omega \approx \pm 24.5~\Omega \\
+\end{align*}
+#@HiddenEnd_HTML~656Res,Result~@#
 </WRAP></WRAP></panel>