Star/Wye electrical connection math symbol

TikZ? (Scalable line width added, great thanks to marmot!)

\documentclass{article}
\usepackage{tikz}
\usepackage{amssymb}
\newcommand{\wye}{\mathbin{\tikz[x=1ex,y=1ex]{\draw[line width=.1ex] (0,0)--(45:1)--++(-45:1) (45:1)--++(0,1);}}}
\begin{document}
$1\wye2$ {\Huge $1\wye2$}
\end{document}

\documentclass{article}
\usepackage{tikz}
\usepackage{amssymb}
\newcommand{\wye}{\mathbin{\tikz[x=1ex,y=1ex]{\draw[line width=.1ex] (0,0)--(30:1)--++(-30:1) (30:1)--++(0,1);}}}
\begin{document}
$1\wye2$ {\Huge $1\wye2$}
\end{document}

I made one leg a bit thicker, in the manner of \Delta.

Works across math styles.

\documentclass{article}
\usepackage{rotating,stackengine,scalerel}
\newcommand\wye{\scalerel*{\stackengine{-1pt}{%
  \rotatebox[origin=c]{30}{\rule{10pt}{.9pt}}\kern-1pt%
  \rotatebox[origin=c]{-30}{\rule{10pt}{1.3pt}}}{%
  \rule{.9pt}{10pt}}{O}{c}{F}{F}{S}}{\Delta}}
\begin{document}
$\Delta\wye
\scriptstyle\Delta\wye
\scriptscriptstyle\Delta\wye$
\end{document}

Merely changing the instances of {30} and {-30} to {40} and {-40} will change the aspect, while scalerel will take care of the scaling automatically: