Microdischarge detection in high frequency capacitors

Higher frequency power is playing an increasingly important role in the power conditioning and high power electronics areas. This is evident in manv new applications of high frequency devices such as sw'itching power supplies, radar modulators, and numerous pulsed power applications. Multi-factor stressing and related erosion of the dielectric material from microdischarges form a dominant cause of device failure, and this insulation deterioration can be accelerated under higher frequency stressing. The methods developed to investigate component failure have been established in the past by 60 Hz system requirements. Conventional detection systems are designed for dc, 60 Hz, and 400 Hz, but cannot generally be applied at high frequencies. This lack of high frequency diagnostic capabilities has contributed to a poor understanding of aging processes and failure mechanisms in new high frequency devices. To help researchers understand the fundamental aging processes and reliably be able to predict service lifetimes, new tools that can detect and analyze microdischarge activity under high frequency conditions are being developed. This paper describes the design of a new microdischarge detection technique that can be used at high frequencies, and it's application to capacitors. This technique uses a series resonant multikilohertz power system in which the primary capacitance is two capacitors under test. Preliminary assessment of this new detection technique have validated its applicability to high frequency components. Initial test data and it's relevance will be discussed in detail. This new detection technique offers a multi-spectral diagnostic capability which will help advance scientific understanding of the fundamental aging processes under the high frequency conditions for which the devices are designed.