\input{Preambule}%

\begin{document}
\begin{tikzpicture}[%
    show background rectangle,%
    tight background,%
    background rectangle/.style={fill=white}%
  ]
  \tikzset{%
    point/.pic={%
      \fill[black] (0,0) circle[radius=0.05];%
    }%
  }%

  %
  % Conducteurs
  %
  \coordinate (wire center) at (0,-1);%
  \path[draw=black] (wire center) pic {point} circle[radius=3.5];%

  % Neutre
  \path (wire center) ++(135:1.75) coordinate (n center);%
  \draw (n center) circle[radius=0.90];%
  \path (n center) pic {point} node[below right] {N};%

  % Phases
  \foreach \x/\y/\z/\p in {a/-135/A/above right,b/-45/B/below,c/45/C/above} {%
      \path (wire center) ++(\y:1.75) coordinate (\x\space center);%
      \draw (\x\space center) circle[radius=1.1];%
      \path (\x\space center) pic {point} node[\p] {\z};%
    }%

  %
  % Annotations
  %
  % Exterior diameter
  \draw[{Latex[]}-{Latex[]}] (wire center) ++(-4,-3.5)%
  coordinate (bottom dext)%
  -- ++(0,7) coordinate(top dext)%
  node[midway, left] {$d_{\mathrm{ext}}$};%
  \draw[dashed] (wire center) ++(0,3.5) -- (top dext);%
  \draw[dashed] (wire center) ++(0,-3.5) -- (bottom dext);%

  % External diameter divided by 4
  \draw[{Latex[]}-{Latex[]}] (wire center) -- ++(180:1.75) %
  node [pos=1, left] {$\dfrac{d_{\mathrm{ext}}}{4}$};%
  \draw[dashed] (wire center) circle[radius=1.75];%

  % Arc
  \draw[dashed] (wire center) -- ++(45:4);%
  \draw[dashed] (wire center) -- ++(-45:4) coordinate (start arc);%
  \draw[{Latex[]}-{Latex[]}] (start arc) arc[start angle=-45, end angle=45, radius=4]%
  node [midway, right] {$\dfrac{\pi}{2}$};%

  % Radius neutral
  \draw[{Latex[]}-{Latex[]}] (n center) -- ++(135:0.9) node[midway, above right] {$R_{\nrm}$};%

  % Radius phase
  \draw[{Latex[]}-{Latex[]}] (a center) -- ++(-135:1.1) node[midway, above left] {$R_{\arm}$};%
\end{tikzpicture}
\end{document}
% Local Variables:
% mode: latex
% TeX-engine: luatex
% TeX-source-correlate-method-active: synctex
% ispell-local-dictionary: "british"
% coding: utf-8
% LaTeX-indent-level: 2
% fill-column: 120
% End:
