Considered in this paper are development and creation of high-power LED luminaires with high light efficiency and color rendering index (CRI). As light sources, there used are 6 powerful LED СОВ (Chip-on-Board) modules CreeCXA 2550, the radiation of which contains quasi-chromatic peaks in the spectral range 600…650 nm. It allows to provide CRI values higher than 92. Features of the improved compact construction of the luminaire with indicated COB modules have been presented. To ensure normal thermal regimes of LED COB modules, a small cooling system based on heat pipes has been created, the optimal dimensions of the structural elements of which have been determined by computer simulation. The results of modeling and experimental studies have shown that the developed and manufactured passive cooling system of LED COB modules provides operation temperature modes (up to 85 °C) of light-emitting crystals at the total electric power of COB modules up to 290 W and allows using the luminaires of this type in the systems of continuous artificial illumination with combined power supply. The efficiency of the developed cooling system at some angles to the horizon expands the scope of applying the illumination device.