94_aging_hf_hv - 1034 IEEE Transactions on Dielectrics and...

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1034 IEEE Transactions on Dielectrics and Electrical Insulation Vol. 1 No. 6, December 1994 Determination of Aging-model Constants under High Frequency and High Electric Fields W. Khachen and J. R. Laghari Department of Electrical and Computer Engineering, State University of NewYork, Buffalo NY ABSTRACT Polypropylene film is tested for life under HV, frequencies up to 30 kHz, and aging and breakdown studies are conducted. The life data obtained is applied to three different aging models relating electric stress to time to failure: the inverse power, the exponential and the thermodynamic model. The dependency of the constants of these models on the frequency of the applied voltage is determined. The results show that the aging model constants are dependent on applied voltage and frequency. 1. INTRODUCTION a large number of future aerospace and space F"" power applications, such as in high power satellites, radars and microwaves, the use of much higher voltages and frequencies will be required [l]. These applications will place much greater stress on the power storage and transport components used in such systems. Presently, there are many components in the high power electronics industry (-J 1 kV) that operate at frequencies ranging from 1 to N 50 kHz [2]. High frequency is also used widely in low voltage electronics and power equipment in the aerospace and electronics industry where the main production items are power supplies, transmitters and equipment [3]. With a need for increasing the operating voltage for these applications, there is a growing need to understand fully the behavior of electrical insulation when exposed to high frequency HV conditions. Different polymers have been studied extensively at HV and at high frequency ranging from 50 HZ to - 30 kHz [3-61. It is believed that the deterioration pro- cess increases due to acceleration of partial discharges and heat build-up in the voids and microcavities of the insulating material when the frequency is increased [7- lo]. Also, the rate of degradation varies from one poly- mer to other. No theory and no fitting of experimental data to any of the available aging models is reported in the literature. 2. AGING MODELS Three major models relating the test stress with the time to failure are commonly accepted: the inverse power model, the exponential model and the thermodynamic model, as described below. 2.1. INVERSE POWER MODEL The inverse power model one of the most frequently used in the aging studies under electrical stress only. It is given by [11] L = kV-" (1) where L is the time to failure (usually it is a Weibull scale parameter, the mean or some percentile), V the applied voltage, and k, n are constants determined from experimental data. 2.2. EXPONENTIAL MODEL The basic form of this model is given by [ll] where c, B are constants determined from experimental data. 1070-9878/94/$3.00 @ 1994 IEEE Authorized licensed use limited to: INDIAN INSTITUTE OF TECHNOLOGY KANPUR. Downloaded on August 11,2010 at 12:20:11 UTC from IEEE Xplore. Restrictions apply.
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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.

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94_aging_hf_hv - 1034 IEEE Transactions on Dielectrics and...

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