Power/Loss diagram

With the to [out=...,in=...] syntax one can make the corners smoother.

\documentclass[tikz,border=20pt]{standalone}
\usepackage{mathptmx}
\usepackage[outline]{contour}
\usetikzlibrary{calc,arrows.meta,patterns,backgrounds}

\begin{document}

\begin{tikzpicture}
\shade[left color=black!10, right color=black!80]
(0,0)-- ++(1,0) to [out=0,in=90] 
++(0.2,-0.25) --  ++(-0.25,0)-- ++(0.5,-0.5) node[anchor=north]{$P_{cus}(t)$}
-- ++(0.5,0.5) -- ++(-0.25,0) to [out=90,in=180] ++(0.3,0.5)-- ++(0.7,0)to [out=0,in=90]
++(0.2,-0.25)-- ++(-0.25,0)-- ++(0.5,-0.5) node[anchor=north]{$P_{fe}(t)$}
-- ++(0.5,0.5)-- ++(-0.25,0)to [out=90,in=180] ++(0.3,0.5)-- ++(1.7,0)to [out=0,in=90] 
++(0.2,-0.25)-- ++(-0.25,0)-- ++(0.5,-0.5) node[anchor=north]{$P_{cur}(t)$}
-- ++(0.5,0.5)-- ++(-0.25,0)to [out=90,in=180] ++(0.3,0.5)-- ++(1.7,0)to [out=0,in=90]
++(0.2,-0.25)-- ++(-0.25,0)-- ++(0.5,-0.5) node[anchor=north]{Perdas por atrito} 
-- ++(0.5,0.5)-- ++(-0.25,0)to [out=90,in=180] ++(0.3,0.5)-- ++(0.7,0)to [out=0,in=90]
++(0.2,-0.25)-- ++(-0.25,0)-- ++(0.5,-0.5) node[anchor=north]{Outras perdas} 
-- ++(0.5,0.5)-- ++(-0.25,0)to [out=90,in=180] ++(0.3,0.5)-- ++(0.7,0)-- 
++(0,-0.5)-- ++(1.5,1.5) node[anchor=west]{$P_o(t)$} -- ++(-1.5,1.5)-- ++(0,-0.5)-- (0,3.25)-- ++(0,-3.25);

\draw (0.0,1.5) node[anchor=east]{$P(t)$};
\draw[thick, dashed] (4.50,0)--(4.50,3.75) node[anchor=south]{Entreferro};
\draw[thick, dashed] (7.2,0.25)--(7.2,3.75) node[anchor=south]{$P_e(t)$};
\end{tikzpicture}

\end{document}

\documentclass[tikz,border=20pt]{standalone}
\usepackage{mathptmx}
\usepackage[outline]{contour}
\usetikzlibrary{calc,arrows.meta,patterns,backgrounds}

\begin{document}

\begin{tikzpicture}
\shade[left color=black!10, right color=black!80]
(0,0)-- ++(1,0) to [out=0,in=90] 
++(0.2,-0.25) --  ++(-0.25,0)-- ++(0.5,-0.5) node[anchor=north]{$P_{cus}(t)$}
-- ++(0.5,0.5) -- ++(-0.25,0) to [out=90,in=0] ++(-0.25,0.5)-- ++(1,0)to [out=0,in=90]
++(0.2,-0.25)-- ++(-0.25,0)-- ++(0.5,-0.5) node[anchor=north]{$P_{fe}(t)$}
-- ++(0.5,0.5)-- ++(-0.25,0)to [out=90,in=0] ++(-0.25,0.5)-- ++(2,0)to [out=0,in=90] 
++(0.2,-0.25)-- ++(-0.25,0)-- ++(0.5,-0.5) node[anchor=north]{$P_{cur}(t)$}
-- ++(0.5,0.5)-- ++(-0.25,0)to [out=90,in=0] ++(-0.25,0.5)-- ++(2,0)to [out=0,in=90]
++(0.2,-0.25)-- ++(-0.25,0)-- ++(0.5,-0.5) node[anchor=north]{Perdas por atrito} 
-- ++(0.5,0.5)-- ++(-0.25,0)to [out=90,in=0] ++(-0.25,0.5)-- ++(1,0)to [out=0,in=90]
++(0.2,-0.25)-- ++(-0.25,0)-- ++(0.5,-0.5) node[anchor=north]{Outras perdas} 
-- ++(0.5,0.5)-- ++(-0.25,0)to [out=90,in=0] ++(-0.25,0.5)-- ++(1,0)-- 
++(0,-0.5)-- ++(1.5,1.5) node[anchor=west]{$P_o(t)$} -- ++(-1.5,1.5)-- ++(0,-0.5)-- (0,3.25)-- ++(0,-3.25);

\draw (0.0,1.5) node[anchor=east]{$P(t)$};
\draw[thick, dashed] (4.0,0)--(4.0,3.75) node[anchor=south]{Entreferro};
\draw[thick, dashed] (6.5,0.25)--(6.5,3.75) node[anchor=south]{$P_e(t)$};
\end{tikzpicture}

\end{document}

One could also just switch on and off rounded corners along the path. The advantage is that one does not need to know the angles of the path.

\documentclass[tikz,border=20pt]{standalone}
\usepackage{mathptmx}
\begin{document}
\begin{tikzpicture}
\shade[left color=black!10, right color=black!80]
    (0,0)[rounded corners]-- ++(1,0)[sharp corners]  --
    ++(0,-0.25)  -- ++(-0.25,0) -- ++(0.5,-0.5) node[anchor=north]{$P_{cus}(t)$} 
    -- ++(0.5,0.5)-- ++(-0.25,0)[rounded corners] -- ++(0,0.5)-- 
    ++(1,0)[rounded corners=0]--
    ++(0,-0.25)-- ++(-0.25,0)-- ++(0.5,-0.5) node[anchor=north]{$P_{fe}(t)$} -- ++(0.5,0.5)
    -- ++(-0.25,0)[rounded corners]-- ++(0,0.5)-- ++(2,0) [sharp corners]--
    ++(0,-0.25)-- ++(-0.25,0)-- ++(0.5,-0.5) node[anchor=north]{$P_{cur}(t)$} 
    -- ++(0.5,0.5)-- ++(-0.25,0)[rounded corners]-- ++(0,0.5)-- ++(2,0) [sharp corners]--
    ++(0,-0.25)-- ++(-0.25,0)-- ++(0.5,-0.5) node[anchor=north]{Perdas por atrito} -- ++(0.5,0.5)
    -- ++(-0.25,0)[rounded corners]-- ++(0,0.5)-- ++(1,0)[sharp corners]--
    ++(0,-0.25)-- ++(-0.25,0)-- ++(0.5,-0.5) node[anchor=north]{Outras perdas} -- ++(0.5,0.5)
    -- ++(-0.25,0)[rounded corners]-- ++(0,0.5)-- ++(1,0)[sharp corners]-- 
    ++(0,-0.5)-- ++(1.5,1.5) node[anchor=west]{$P_o(t)$} -- ++(-1.5,1.5)
    [rounded corners]-- ++(0,-0.5)[sharp corners]
    -- ++(-10.5,0)-- ++(0,-3.25);

    \draw (0.0,1.5) node[anchor=east]{$P(t)$};
    \draw[thick, dashed] (4.0,0)--(4.0,3.75) node[anchor=south]{Entreferro};
    \draw[thick, dashed] (6.5,0.25)--(6.5,3.75) node[anchor=south]{$P_e(t)$};
\end{tikzpicture}
\end{document}