The highest activity of brain waves concerns the beta band in the frequency range of 21-22Hz, regardless of the type of the light source (LED, fluorescent tube). The methods used to supply power and color temperature of fluorescent tubes do not significantly affect bioelectrical brain activity during "work", but previous lighting with fluorescent tubes during work has an essential effect on bioelectrical brain activity during rest. Regardless of the color temperature, LED lighting with PWM power supply leads to the highest bioelectrical activity (mainly in the range of 21-22Hz) in the brain during work and rest, which might suggests the usefulness of this method of supplying power for everyday work. Incandescent light does not affect the bioelectrical brain activity during work and rest.

The popularity of LED-based luminaires has increased enormously in recent years. Every such luminaire consists of several elements including a polymer-based transparent housing, yet some of the ageing aspects of specific luminaire materials have not been investigated. In this paper, we present research aimed at determining the impact of LED lamp powering mode on polymer material deterioration. In the experiment, three LED lamp operating systems based on two different pulse width modulation units and one DC power source were used to induce deterioration in a polymethyl methacrylate sample. Two types of LEDs, white and ultraviolet, were considered as the most significant in terms of the impact on the material. Observations of the surface's morphological changes were performed to enable non-destructive investigation of the degradation of the exposed samples. In order to obtain high roughness detection sensitivity, atomic force microscopy was used. We observed various ageing ratios of the material, despite the fact that total average optical energy for specific wavelengths was equal for all samples. The importance of these findings for designing modern luminaires is discussed.

In the paper self-exciting induction generator system has been presented. It has been made on the base of cage induction motor, and it is intended for small hydroelectric and wind power plants. The basic advantages of the system are reliability, simple construction, and durability as well self-service and low cost of production. In the presented solution, generator is not connected with distribution system and represents an autonomous system. For voltage and frequency stabilization purpose its works with AC/DC converter. The paper presents the result of simulation research, as well experimental result obtained on laboratory model of generator with converters and prediction control.

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Abstract. This paper presents investigation of methods for reducing light pulsation and plasma temperature inside a high intensity discharge (HID) lamp arc tube. Differences found in light emission of an arc tube plasma channel under different power supply methods are presented and discussed in this work. The novelty of the paper lies in systematical investigation of different power converter supply methods and demonstrating that it has a significant influence on plasma temperature in an arc tube. The tested lamp was powered by electronic ballasts controlled by different algorithms, which forced their current waveform. To compare the results, the authors performed measurements on a discharge lamp powered by a standard electromagnetic ballast. The investigation of plasma parameters is based on the optical spectroscopy method. It was shown that by using the appropriate current shape of a high switching frequency supply converter, the plasma temperature of an HID lamp can be reduced almost by half.Key words: plasma temperature, electronic ballast, electromagnetic ballast, lamp current, light flux, light pulsation, high intensity discharge lamp.Investigation of HID-lamp light emission differences for different power supply methods Therefore, authors decided to perform a research determining the aforementioned parameters of an HID lamp. Plasma theoryPlasma is a source of optical radiation. One of the methods used to examine this state of matter is optical spectroscopy. The spectrum of plasma radiation carries a lot of information about atoms or ions, such as the type of gases used in discharge lamps, and the conditions in which they are located. All the processes taking place in radial plasma can be interpreted as a transition between two different quantum energy states. Processes involving the radiation of electrons and atoms (or ions) occur when an electron moves in an electrical field from one charged particle to another, usually an ion. As a result of its interaction with this particle, part of the path of the electron is curved. The temperature inside the arc tube of a discharge lamp is the parameter that determines the appropriate spectral distribution of the energy emitted by the plasma discharge, and the corresponding luminous efficiency. In the radiation spectrum of an HID lamp, there are a number of lines, characteristic of excited atoms. The shape of the spectral line reveals the conditions (pressure and temperature) prevailing in the discharge lamp. Fig. 1 shows a view of luminous plasma in a cold arc tube, whereas Fig. 2 shows luminous plasma in a hot arc tube.