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Prof. Marek Hartman
THE USE OF SERIES FOURIER IN ANALYSING PWM MODULATION
In the paper there is presented a basic mathematic series Fourier for one and two variables. Given are the criteria of the convergences of the sum of the parts of the series Fourier in the case of one and two variables. The use of series Fourier of one and two variables is presented with the support of Bennett transformation for the product of two functions. Given is a description of the PWM impulse modulation with the use of Bennett transformation. Included is a description of PWM modulation used in a multiple level inverter. Mathematical analysis is illustrated by results from computer simulation and graphics.
Prof. Zygmunt Ku¶mierek
HARMONICS IN ELECTROMAGNETIC SYSTEMS
Classfication of harmonics: higher harmonics, interharmonics, subharmonics. Source of harmonics. Means of characterising the effects of harmonics in electrical signals. Identification of harmonic sources. Results of the appearance of harmonics: the influence of harmonics on the parameters of the quality of electrical energy, the reaction of harmonics on the accuracy of measuring electrical power and energy. Criteria for connecting to the power grid nonlinear load, which are sources of harmonics. Locating and measuring harmonics in the electrical system.
Prof. Igor V. Zhezhelenko
ELECTRICITY SUPPLY RELIABILITY IN NON-SINUSOIDAL MODES
In this paper the impact of harmonic distortion on the life span and functional reliability indices of power transformers, induction motors and cables is considered. The thermal and electrical stresses on insulation aging of power system equipment in non-sinusoidal operating conditions are taken into account. The detrimental effects of harmonics on equipment are analyzed using both deterministic and probabilistic approach. Expressions for the derating factors must be introduced to prevent a premature failure of main components of industrial energy systems in distorted regime are presented. It is shown that the loss in reliability of power system equipment at voltage harmonic distortion is caused mainly by electrical stress. Finally, numerical examples are presented and some applications of proposed approach are discussed.
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