The use of non-linear loads in transformers leads to increased losses, heat and more vibration and noise are generated. Vibrations should be investigated because they cause to decrease the nominal values of the transformer and its service life. Figure A shows the variation of core vibration with respect to these harmonic components with current harmonic components of linear load, 3-phase and 1-phase rectifier, respectively. Figure A. Signals obtained according to load condition a) current harmonic spectrum, b) axial acceleration harmonic spectrum Purpose: It is aimed to investigate the vibration signals of a dry type isolation transformer core which operates different load conditions. Theory and Methods: Transformer and loads are modelled and simulated by using ANSYS Maxwell and Simplorer. And then core forces obtained from Maxwell are used as input parameters in ANSYS Mechanical. Finally, vibration signals as harmonic responses are obtained. Results: Increase in the THD value leads to an increase in the number and amplitude of vibration harmonic components. With the increase in the THD value, the second and third harmonic components of the vibration have increased in amplitude. It has been shown that the increase of the THD value caused by using the 1-phase rectifier leads to only the increase of the peak value amplitude in the radial force frequency spectrum, there is no similar increase in the axial force frequency spectrum. Conclusion: The increase of the THD value, the fundamental components of the vibration signals in the axial direction the second and third harmonic component amplitudes are increased. Also, the increase in THD value has led to a greater number of regional maximum points depending on the grades of the harmonic currents in the vibration frequency spectrum. Vibration signals must be carefully monitored since vibrations in the axial direction may cause a failure such as core deformation on the transformer.
The electromagnetic behavior of the inductors used as passive circuit elements directly affects the electrical and mechanical performance of the power electronics circuits. In general, when using inductor core structures with/without airgap length in the classical design process, the dynamic effects of the inductance value are not considered in the design stage. However, the inductance value may change during the operation of the circuit due to electrical and magnetic parameters of the inductor, and this change is called roll-off value of the inductance. In this study, the roll-off value has been determined graphically and numerically based on mechanical parameters (such as air-gap length) and electrical parameters (such as winding turns and DC current amplitude) for an air-gapped ferrite E core designed with finite element analysis (FEA) software. Thus, not only the inductance value has been calculated in the design stage but also the roll-off value during the operation of the circuit has been reported with the parametric simulation studies.
In this paper, 4-phase interleaved buck converter is simulated and implemented by using 16 bit dsPIC30F2020 microcontroller. Proposed interleaved buck converter can operate as a single converter or interleaved converter mode. It shares the load current, and changes its switching frequency according to operation mode to achieve same ripple effect in interleaved converter mode. Before implementation stage firstly, the saturation effect of inductors and performance of converter have been tested and the system is simulated with co-simulation carried out with MATLAB/Simulink and FEM-based software. The data obtained from FEM-based software and Simulink is compatible with each other. Finally whole system is implemented and the advantages of the proposed converter structure have been presented based on comparison of simulated and experimental results with a traditional buck converter. It is seen that output current ripple, EMI level and voltage stress on components are reduced with proposed interleaved converter.
Ozetge-Gii'r kalitesi problemleri, �ebekeden beslenen cihazlarm gorevini tam olarak yapamamasma, yanh� 'rah�masma ve en kotiisii bozulmalarma neden olabilirler. Bu problemler, �ebeke gerilimi ve/veya 'rekilen aklmm dalga formundaki anhk veya siirekli olacak �ekilde bozunumlardlr.
Ara-harmonikler, güç sistemlerinde doğrusal olmayan yüklerden, asenkron anahtarlamanın yapıldığı anahtarlamalı sürücülerden veya geçici durumda çalışan yüklerdeki hızlı akım değişikliklerinden kaynaklanmaktadır. Böyle çalışma koşulları altındaki transformatör nüvelerinde doymanın meydana gelmesi ve aşırı ısınma gibi problemlerin yanında titreşim seviyelerinin anormal seviyelerde artması gibi mekanik problemler de ortaya çıkmaktadır. Buna karşılık, ara-harmoniklerin yol açtığı titreşimlerdeki anormal artışın incelendiği çalışma sınırlı sayıdadır. Ara-harmoniklerin transformatör nüvesinin titreşimi üzerindeki etkilerini belirlemek amacıyla bu çalışmada bir-fazlı 10 kVA anma gücündeki bir yalıtım transformatörünün nüvesindeki titreşim yer değiştirmesi değerleri çeşitli ara-harmonik frekanslarına sahip uyarımlar altında incelenmiş ve sonuçları karşılaştırılmıştır. Yapılan benzetim çalışmalarında, ara-harmonik frekansına bağlı olarak titreşim harmonik spektrumunda yan-bantlar şeklinde veya çift katları olacak şekilde bileşenler oluştuğu ancak bazı ara-harmonik frekanslarında ise kesirli frekanslarda bileşenlerin ortaya çıkmasına yol açtığı sonucu elde edilmiştir.
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