Optical , J , and K photometric observations of the KV UMa black hole X-ray nova in its quiescent state obtained in 2017-2018 are presented .
A significant flickering within light curves was not detected , although the average brightness of the system faded by \approx 0.1 ^ { m } during 350 days .
Changes in the average brightness were not accompanied with the increase or the decrease of the flickering .
From the modelling of five light curves the inclination of the KV UMa orbit and the black hole mass were obtained : i = 74 ^ { \circ } \pm 4 ^ { \circ } , M _ { BH } = ( 7.06 \div 7.24 ) M _ { \odot } dependently on the used mass ratio .
The non-stellar component of the spectrum in the range \lambda = 6400 \div 22000 Å can be fitted by a power law F _ { \lambda } \sim \lambda ^ { \alpha } , \alpha \approx - 1.8 .
The accretion disk orientation angle changed from one epoch to another .
The model with spots on the star was inadequate .
Evolutionary calculations using the ‘ ‘ Scenario Machine ’ ’ code were performed for low mass X-ray binaries , a recently discovered anomalously rapid decrease of the orbital period was taken into account .
We showed that the observed decrease can be consistent with the magnetic stellar wind of the optical companion which magnetic field was increased during the common envelope stage .
Several constraints on evolutionary scenario parameters were done .