Semiconductor light sources are currently the fastest growing and most energy efficient group of light sources used in lighting technology. Their lighting parameters, such as luminous flux, correlated color temperature and color rendering index depend on the value of the forward current, as well as the temperature of the junction. LED source manufacturers usually specify, in data sheets, the effect of junction temperature and forward current on the luminous flux for individual light sources. The difficulty, however, is the correct determination of temperature and then lighting parameters, by simulation methods for multi-source lighting systems. Determining the junction temperature which affects lighting parameters is particulary important in the case of LED panels and luminaires, where thermally coupled LED sources shaping the output lighting parameters are in close proximity to each other. Additionally, other factors influencing the temperature distribution of sources, such as the design and geometry of the cooling system, the design of the printed circuit and thermal interface material used, should be considered. The article is a continuation of the publication in this journal where the influence of factors influencing the temperature distribution of the LED panel is presented. The purpose of the research in this article was to confirm the possibility of using CFD (Computational Fluid Dynamics) software, as well as to determine the accuracy of the results obtained in the temperature analysis of the multi-source LED panel, and in determining the output lighting parameters of the LED panel based on it. In this article, based on previously published research, a LED panel model with a cooling system was made, and then the CFD software determined the junction temperature of all light sources. The determined temperature of the LED sources constituted the basis for determining the output lighting parameters of the panel: luminous flux, color temperature and color rendering index. The simulation results were verified by real measurements on the constructed LED panel prototype. The LED panel temperature difference between the simulation results and the real results on the prototype did not exceed 5%. Moreover, the error of lighting parameters between the simulation results obtained and the results on the LED panel prototype in the worst case was 4.36%, which proves the validity and accuracy of simulation studies.

Limiting junction temperature T j and maintaining its low value is crucial for the lifetime and reliability of semi-conductive light sources. Obtaining the lowest possible temperature of T j is especially important in the case of LED panels, where in a short distance there are many light sources installed, between which there occurs mutual thermal coupling. The article presents results of simulation studies connected with the influence of construction and ambient factors that influence the value of junction temperature of exemplary LED panel sources. The influence of radiator's construction, printed circuit boards, as well as the influence of ambient factors, such as ambient temperature T a and air flow velocity v were subjected to the analysis. Numerical calculations were done in the FloEFD software of the Mentor Graphics company, which is based on computational fluid dynamics (CFD). For construction of the LED thermal panel model the optical efficiency η o and real thermal resistance Rth j-c were determined in a laboratory for the applied light sources.

This paper focuses on the matter of cogging torque reduction by combining various methods of cogging torque minimization. Due to the high costs of prototype construction, cogging torque is minimized during the design phase by using numerical methods, while computer simulations are used to find a magnetic circuit arrangement for which the cogging torque has the smallest possible value. Cogging torque occurs as a result of combined impact of the magnetic field of a permanent magnet located at rotor and stator with variable magnetic conductivity depending on an angle of rotation. It is a pulsating torque and occurs permanently during machine operation, impacting the operation of the entire device cooperating with the electric machine and causing vibrations, tension, and noise. It results in braking torque and subsequent power losses and leads to faster wear and tear of machine structural elements. High cogging torque values cause problems with rotational speed adjustment. In the case of electric generators used in wind power plants, it impedes the start-up of power plants at high wind speeds. Considering the above, the reduction of cogging torque in permanent-magnet machines is extremely important.

The field of indoor lighting covers a wide range of lighting uses with varying requirements for lighting conditions to be satisfied by properly selected lighting equipment. The need to frequently change the arrangement of useable areas entails the necessity to adapt the lighting to new requirements. A good solution for reducing costs and saving time is a luminaire adjusting the luminous flux and spatial luminous intensity distribution in a wide range. The authors present the concept of an adaptive luminaire and its construction assumptions. In addition, the results of studies on the development of the concept are shown together with conditions and limitations that influenced the construction of the luminaire. The analysis of the surface of the moveable reflector is presented, and the results of testing the luminaire prototype are compared with the results of simulation tests.

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