  We present the photometric analysis of \textit{BVR} and \textit{TESS} light
curves of three eclipsing binaries (RU~UMi and purely studied VY~UMi, GSC
04364-00648), together with their period changes considering archival data and
new minima times from our and \textit{TESS} observations. For the first time we
detected wave-like variations with low-amplitude in $O-C$ residua of RU UMi,
which can be interpreted as a consequence of the light-time effect caused by
the 3rd invisible component with period 7370 days. Period increase with rate
2.56(9)$\times10^{-7}$~d/yr$^{-1}$ detected in the VY UMi system corresponds to
mass transfer from the secondary to the primary component. For GSC 04364-00648
binary system we find some quadratic changes on the $O-C$ diagram, which
corresponds to a period decrease with a high rate of
$-2.26(5)\times10^{-5}$~d/yr$^{-1}$. We cannot assumptions about their nature,
mainly due to short time of observation and uneven coverage of $O-C$ diagram.
We also determined the absolute parameter of their components using the
photometric solution and \textit{GAIA} distances.
