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On the distribution of AC and DC winding capacitances in high-frequency power transformers with rectifier loads
KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.ORCID iD: 0000-0002-1755-1365
2011 (English)In: IEEE Transactions on Industrial Electronics, ISSN 0278-0046Article in journal (Refereed) Published
Abstract [en]

In this paper a method to adjust the AC winding capacitance of high-voltage high-frequency transformers by means of a winding-rectifier integration is described. First a theoretical background to the method is given. From the theory, an equivalent circuit describing the characteristics of the combination of the transformer and the rectifier is derived. The derived circuit introduces the concept of a DC-capacitance. Finally, the equivalent circuit and the method itself are verified by means of experiments on a transformer-rectifier system from an industrial application with the ratings 70 kV, 30 kW, 25 kHz. The results from the experiments show that it is possible to vary the AC component of the winding capacitance from a few percent up to 95 percent of the total winding capacitance. This means that it is virtually free to choose between AC or DC capacitance during the design stage. This is very important in applications such as resonant converters with transformers having secondary windings connected to rectifiers with capacitive output filters.

Place, publisher, year, edition, pages
Keyword [en]
Capacitance, Converters, Equivalent circuits, Integrated circuit modeling, Power transformers, Rectifiers, Windings, high-voltage conversion, resonant converters, transformer parasitics, winding capacitance
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
URN: urn:nbn:se:kth:diva-25218DOI: 10.1109/TIE.2010.2055773ISI: 000289478000030ScopusID: 2-s2.0-79954464727OAI: diva2:356577
QC 20101013Available from: 2010-10-13 Created: 2010-10-13 Last updated: 2011-05-02Bibliographically approved
In thesis
1. Control and Design Aspects of Components and Systems in High-Voltage Converters for Industrial Applications
Open this publication in new window or tab >>Control and Design Aspects of Components and Systems in High-Voltage Converters for Industrial Applications
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

High-frequency dc-dc converters are widely used in power electronic applications, both in consumer products and industrial products. By operating the converter at higher frequencies both a smaller size and better control characteristics can be obtained.

It is the objective of this work to investigate how high-frequency power converters can be optimized for high-voltage industrial applications. Specifically, power supplies for electrostatic precipitators (ESP) are considered. The work refers to operating frequencies higher than 20 kHz and load voltages reaching 100 kV and above. The power handling capability ranges from 10 to 200 kW.

High-frequency power supplies were originally introduced on the ESP market in 1993. An evaluation of the experiences gained during the first decade of operation is presented. It was found that the dust emissions have been reduced at the majority of the installations.

Efficiency aspects like IGBT losses in soft-switching operation with a sinusoidal collector current and the influence of different control methods have been analyzed. Dynamic properties of the IGBT such as: dynamic conduction losses and dynamic tail charges are presented and experimentally verified. The IGBT losses have been evaluated for LCC-converters operating above the resonance frequency. The losses have been measured and compared for different control methods and for different turn-off strategies, zero-current-switching and zero-voltage-switching, respectively. It is shown experimentally that the LCC-converter is more efficient than the series-loaded resonant converter for a range of values of the parallel capacitance. This is because the LCC-converter allows a lower turns ratio of the transformer.

The high-voltage high-frequency transformer has been analysed with respect to its parasitic elements. A method is presented, integrated rectification, which enables a sub-division of the winding capacitance into an AC-part and a DC-part. It is validated experimentally that they may be utilized as circuit elements and that the ratio of these capacitances may be varied within a wide range. This method is considered to be of importance when optimizing converters utilizing topologies where the output rectifier is followed by a capacitive filter.

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. xii, 85 p.
Trita-EE, ISSN 1653-5146 ; 2010:038
High-voltage converter, resonant converter, high-voltage transformer, transformer parasitics, IGBT, soft-switching, control
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
urn:nbn:se:kth:diva-25280 (URN)978-91-7415-757-4 (ISBN)
Public defence
2010-10-29, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
QC 20101014Available from: 2010-10-14 Created: 2010-10-14 Last updated: 2010-10-14Bibliographically approved

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