方波电压叠加高次谐波对环氧树脂绝缘短时击穿的影响

The breakdown characteristics of solid insulation under high frequency non-sinusoidal and multi-harmonic is one of the key problems in the design and application of high-frequency transformers with high power density, and there is a lack of research on the influence of square wave voltage superposition harmonic on insulation breakdown. In this paper, the short-time breakdown characteristics of epoxy resin insulation under square wave voltage superimposed with high-order harmonics are studied. Through the measurement platform of insulation breakdown under high-frequency superimposed harmonic voltage, the influences of frequency, temperature and superimposed different harmonics on the insulation breakdown of epoxy resin were studied. The results show that the breakdown strength of epoxy resin decreases with the increase of frequency under bipolar square wave, and the breakdown field strength decreases significantly below 5 kHz. Particularly, a more pronounced decrease in breakdown strength is observed after the superimposition of harmonic voltages. Compared with 50 Hz square wave, the breakdown field strength decreases by 11% when 100 kHz/400 V harmonic is superimposed, and Eb decreases with the increase of harmonic amplitude and frequency. Finally, combined with the free volume breakdown theory, carrier migration and high-frequency AC conductivity model, the influence mechanism of square wave voltage superimposed with high-order harmonics on the breakdown of epoxy resin insulation was studied. The research provides theoretical and experimental bases for insulation design and reliability of high-power solid-state transformer.