PX157 - D3d - inductors in series

\begin{aligned} V_{1} & = L_{1} \frac{d I}{d t} \\ V_{2} & = L_{2} \frac{d I}{d t} \\ V = V_{1} + V_{2} & = (L_{1} + L_{2}) \frac{d I}{d t} \end{aligned}

\begin{aligned} V = L_{e q} \frac{d I}{d t} \\ L_{e q} & = L_{1} + L_{2} \end{aligned}

L_{e q} = \frac{μ N^{2} A_{1}}{l} + \frac{μ N^{2} A_{2}}{l} = \frac{μ N^{2}}{l} (A_{1} + A_{2})