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Obliczanie mocy biernej w modelach matematycznych maszyn elektrycznych prądu przemiennego

Popenda A.

Przegląd Elektrotechniczny

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2017

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R. 93, nr 1

193--196

PL

pracy wykazano, że wartości mocy biernej, obliczone na podstawie składowych wektorów przestrzennych napięcia i prądu zgodnie ze znaną formułą, mogą być ujemne, pomimo że napięcie wyprzedza w fazie prąd. Dotyczy to układów wielofazowych, w tym trójfazowych maszyn prądu przemiennego, w których nastąpiła zmiana kolejności faz. Zaproponowano skorygowaną formułę obliczania mocy biernej układu wielofazowego dla przypadku przeciwnej kolejności faz oraz podano interpretację matematyczną.

EN

In the paper it is shown, that values of reactive power, calculated on the basis of components of voltage and current space vectors in accordance with the well-known formula, may be negative, even though the current is lagging relative to the voltage. This concerns multi-phase systems, incl. three-phase electric machines of alternating current, in which a phase sequence has been reversed. The corrected formula for calculation of reactive power of multi-phase system for the case of reverse phase sequence is suggested and the mathematical interpretation is added.

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Optimization Design of Hybrid Mufflers on Broadband Frequencies Using the Genetic Algorithm

Chiu M-C.

Archives of Acoustics

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2011

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Vol. 36, No. 4

795-822

EN

Recently, there has been research on high frequency dissipative mufflers. However, research on shape optimization of hybrid mufflers that reduce broadband noise within a constrained space is sparse. In this paper, a hybrid muffler composed of a dissipative muffler and a reactive muffler within a constrained space is assessed. Using the eigenvalues and eigenfunctions, a coupling wave equation for the perforated dissipative chamber is simplified into a four-pole matrix form. To efficiently find the optimal shape within a constrained space, a four-pole matrix system used to evaluate the acoustical performance of the sound transmission loss (STL) is eval- uated using a genetic algorithm (GA). A numerical case for eliminating a broadband venting noise is also introduced. To verify the reliability of a GA optimization, optimal noise abatements for two pure tones (500 Hz and 800 Hz) are exemplified. Before the GA operation can be carried out, the accuracy of the mathematical models has been checked using experimental data. Results indicate that the maximal STL is precisely located at the desired target tone. The optimal result of case studies for eliminating broadband noise also reveals that the overall sound power level (SWL) of the hybrid muffler can be reduced from 138.9 dB(A) to 84.5 dB(A), which is superior to other mufflers (a one-chamber dissipative and a one-chamber reactive muffler). Consequently, a successful approach used for the optimal design of the hybrid mufflers within a constrained space has been demonstrated.

3

Currents' Physical Components (CPC) in Circuits with Nonsinusoidal Voltages and Currents. Part 2: Three-Phase Three-Wire Linear Circuits

Czarnecki L. S.

Electrical Power Quality and Utilisation. Journal

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2006

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Vol. 12, nr 1

3-13

EN

This paper summarizes the present state of discussions on power phenomena, power definitions and compensation in three-phase three-wire linear circuits with nonsinusoidal voltages and currents. In particular, definitions of the arithmetic and geometric apparent powers are discussed. It is shown that these two powers result in an erroneous value of power factor of unbalanced loads even if voltages and currents are sinusoidal. A reasoning that leads to a right selection of the apparent power definition is presented as well. The paper also presents the con-cept of the three-phase current decomposition into Currents' Physical Components (CPC) and its application for power definitions and compensation in three-phase circuits.

4

Currents' physical components (CPC) in circuits with nonsinusoidal voltages and currents. Part 1, Single-phase linear circuits

Czarnecki L. S.

Electrical Power Quality and Utilisation. Journal

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2005

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Vol. 11, nr 2

3-14

EN

The paper summarizes the present state of discussions on power phenomena, power definitions and compensation in single-phase linear circuits. The main concepts developed over several decades on how various non-active powers in circuits with nonsinusoidal voltages and currents should be defined and compensated are presented along with a detailed discussion of these concepts. The paper presents also the concept of the single-phase load current decomposition into Currents' Physical Components (CPC) and its application for power definitions and compensation in such circuits. The paper is not addressed to scientists and experts on powers, but rather to common electrical engineers that sometimes face power related problems in nonsinusoidal systems.