Durability Tests on Solid Insulation Materials for Medium Frequency Transformers in the Frequency Range from 1 kHz to 10 kHz

Abstract:
The requirements for insulating materials in high voltage applications are changing due to the use of power electronic components, such as the Power Electronic Transformer. Higher frequency, non-sinusoidal voltages in these components require characterization of the used insulating materials apart from the traditional 50 Hz or 60 Hz ac stresses. Insulation systems must withstand these stresses not only in the short term, but during their entire operating lifetime. Therefore, this paper presents durability tests of three different solid insulating materials at frequencies between 1 kHz and 10 kHz. The paper focuses on the lifetime that can be achieved with voltages from 95% to 60% of the short-time breakdown voltage, as well as the differences between sinusoidal and rectangular voltages. It is found that, for the same percentage of the short-time breakdown voltage, significantly higher lifetimes can be achieved with sinusoidal voltages than with equivalent square-wave voltages.