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[SilasElter] authored and [SilasElter] committed Nov 24, 2024
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28 changes: 17 additions & 11 deletions exercise/tex/exercise04.tex
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\subtask{The input voltage is $U_\mathrm{1}=\SI{760}{\volt}$ at rated power at the output. What is the peak value $\hat I_\mathrm{1}$ of the primary current $i_\mathrm{1}$? What is the peak value $\hat I_\mathrm{2}$ of the secundary current $i_\mathrm{2}$? Calculate the duty cycle of the transistor for this operating case.}

\begin{solutionblock}
To determine the current $\hat I_\mathrm{1}$, the equation for determining the output power \eqref{eq:output power ex04} is primarily used. The unknown energy of the inductance of the primary winding side \eqref{eq:energy primary inductance ex04} is inserted into this equation.
\begin{equation}
P_\mathrm{2} = W_\mathrm{L} f_\mathrm{p}
P_\mathrm{2} = W_\mathrm{L} f_\mathrm{p}, \label{eq:output power ex04}
\end{equation}

\begin{equation}
W_\mathrm{L} = \frac{1}{2}L_\mathrm{1}\hat I_\mathrm{1}^2
W_\mathrm{L} = \frac{1}{2}L_\mathrm{1}\hat I_\mathrm{1}^2. \label{eq:energy primary inductance ex04}
\end{equation}

After substituting, you get this equation:
\begin{equation}
\hat I_\mathrm{1} = \sqrt{\frac{2P_\mathrm{2}}{L_\mathrm{1}f_\mathrm{p}}}= \sqrt{\frac{2\cdot\SI{30}{\watt}}{\SI{760}{\micro\henry}\cdot\SI{50}{\kilo\hertz}}}=\SI{1.257}{\ampere}
P_\mathrm{2} = \frac{1}{2}L_\mathrm{1}\hat I_\mathrm{1}^2 f_\mathrm{p}.\label{eq:output power with IDach ex04}
\end{equation}

\eqref{eq:output power with IDach ex04} must be converted to $\hat I_\mathrm{1}$:
\begin{equation}
\hat I_\mathrm{1} = \hat I_\mathrm{2}
\hat I_\mathrm{1} = \sqrt{\frac{2P_\mathrm{2}}{L_\mathrm{1}f_\mathrm{p}}}= \sqrt{\frac{2\cdot\SI{30}{\watt}}{\SI{760}{\micro\henry}\cdot\SI{50}{\kilo\hertz}}}=\SI{1.257}{\ampere}.
\end{equation}

In an ideal transformer, the energy is maintained between the primary and secondary sides (neglecting losses). To determine the peak value $\hat I_\mathrm{2}$, the known current $\hat I_\mathrm{1}$ and the number of turns of the primary and secondary side can be used. Because of this background, the following equation can be used:
\begin{equation}
\hat I_\mathrm{2} = \hat I_\mathrm{1} \frac{N_\mathrm{1}}{N_\mathrm{2}} = \SI{1.257}{\ampere} \cdot \frac{60}{12} = \SI{6.28}{\ampere}
\hat I_\mathrm{2} = \hat I_\mathrm{1} \frac{N_\mathrm{1}}{N_\mathrm{2}} = \SI{1.257}{\ampere} \cdot \frac{60}{12} = \SI{6.28}{\ampere}.
\end{equation}
Because of CCM the duty cycle $D$ is expressed .....
Because of CCM the duty cycle $D$ is expressed as
\begin{equation}
\frac{U_2}{U_1} = \frac{D^2}{2} \frac{\Delta i_\mathrm{m,max}}{\overline{i}_2} \label{eq:Duty cycle ex04}
\frac{U_2}{U_1} = \frac{D^2}{2} \frac{\Delta i_\mathrm{m,max}}{\overline{i}_2}. \label{eq:Duty cycle ex04}
\end{equation}
Because of the unknown $\Delta i_\mathrm{m,max}$ this value has to be calculate first as
\begin{equation}
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\end{solutionblock}

\subtask{The input voltage is $U_\mathrm{1}=\SI{382}{\volt}$ at nominal load.How much energy is transferred from the input to the output per switching period $\Delta E$ and what is the resulting average power? What happens if there is no ideal voltage source on the output side but an unloaded capacitor and the circuit is operated with $D>0$?}
\subtask{The input voltage is $U_\mathrm{1}=\SI{382}{\volt}$ at nominal load. How much energy is transferred from the input to the output per switching period $\Delta E$ and what is the resulting average power? What happens if there is no ideal voltage source on the output side but an unloaded capacitor and the circuit is operated with $D>0$?}

\begin{solutionblock}

At each switching interval, energy is pushed into the capacitor, the voltage of which continues to rise until a component fails due to a lack of dielectric strength.
\end{solutionblock}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Task 2: Forward converter with asymmetric half-bridge
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