ADE1275Bd01 - IEEE Transactions on Dielectrics and...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
IEEE Transactions on Dielectrics and Electrical Insulation Vol. 11, No. 6; December 2004 1007 Electrically Induced Heat Dissipation in Metallized Film Capacitors M. G. Kong and Y. P. Lee Plasma and Pulsed Power Group Department of Electronic and Electrical Engineering Loughborough University, Loughborough, Leicestershire LE11 3TU, UK ABSTRACT Elevated temperature is a key aging factor for metallized polymer film capacitors with the capacitor life expectancy halved with every 8 8 C of temperature rise. For film capacitors in service, both application of a time-varying external voltage and the extinction of internal breakdown events can deposit significant heat onto the capacitor structure leading to an undesirable temperature rise. Often such heat generation is localized spatially and the resulting temperature gradient enhances the probability of subsequent breakdowns. To facilitate a thorough and generic un - derstanding, a thermal model of metallized film capacitors is developed to simu - late the dynamics of heat generation and transfer under the switching impact of an ( external voltage. Thermal processes in solids polymer layers, electrode coating, and ) zinc-spray segment are modeled with conduction mechanism, whereas convection mechanism is considered for silicone oil and air. Heat generation is induced ei - ther by ohmic losses of the externally applied electric field, or by internal break - down events within the metallized film capacitor structure. This allows a seamless interface between the heat transfer model and the equivalent circuit based field calculation model. Based this electrothermal model, numerical examples are used to study temperature distribution within film capacitors and then to examine the likelihood of localized temperature hot-spots that may lead to spatially preferential breakdowns. Index Terms — Film capacitors, breakdown, heat transfer, film metallization. 1 INTRODUCTION OR numerous industrial applications of metal- F lized film capacitors, there has been a fundamental need to improve their energy density within an increas- ingly compact housing. Inevitably this leads to smaller and smaller design margin with which insulation integrity and system reliability must be ensured. To this end, it is vital to gain a thorough and quantitative understanding of fail- ure mechanisms in metallized film capacitors. This has, over the past three decades, led to wide-ranging investiga- wx tions into a number of key aging factors 1-3 , for example electrical, thermal, and chemical properties of capacitor dielectrics 4, 5 as well as effects of their material degra- dation under mechanical 6 , electrical 7 , and thermal stresses 8 . Extensive studies have also been conducted to establish the effects of the electric and chemical prop- erties of liquid impregnants 9, 10 , and waveforms and peak values of electric stress 11 ] 13 . These studies are Manuscript recei ® ed on 4 October 2002, in final form 27 July 2004.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 06/08/2011 for the course ELECTRICAL 124 taught by Professor Ghjk during the Spring '11 term at Institute of Technology.

Page1 / 7

ADE1275Bd01 - IEEE Transactions on Dielectrics and...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online