APPLICATION OF FOURIER SERIES IN THE ANALYSIS OF NON-SINUSOIDAL ALTERNATING VALUES
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Analyses of alternating electrical circuits in electrical engineering are usually based on assumption that currents and voltages are sinusoidal values. Such assumption allows analysis of electrical networks by symbolic mathematical calculation. It also allows the application of vector diagrams in representing relationship of the analyzed electrical values. In practice, periodic non sinusoidal values are sometimes found. For solving such values symbolic mathematical calculation and vector diagrams cannot be used. In this paper is shown how such non sinusoidal periodic values can be separated, by applying Fourier series, into infinite series which contains a constant term and infinitely many harmonic components. That way allows all the acquired knowledge and methods for solving sinusoidal periodic values to still be used.
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1 Introduction
In various mathematical applications composite functions are approximated by simpler functions that are more suitable for further calculation [1, 2]. In that way, to solve numerous technical and physical problems, periodic functions need to be converted in series according to trigonometric functions, i.e. to display them in the form of a sum of sine and cosine functions of different amplitudes and frequencies [3].
For solving and the analysis of alternating electrotechnical networks it is suitable to use complex calculation, wherein the voltage and the current are shown by phasors. Phasors are composite numbers that are used to display sinusoidal values in a complex plane. The length of those vectors that rotate counter-clockwise with angle velocity represents the maximal value of voltage or current, while the projection of that vector (phasor) on the vertical axis gives the current value of voltage or current. The possibility of application of phasors in the analysis of electrical values is directly dependent on their sinusoidal nature. In case of presence of periodic signals that do not have sinusoidal shape, the conversion of all non-sinusoidal values into sinusoidal is the necessary precondition for using complex calculation in the analysis of alternating circuits
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2 Fourier series
Let