Suppression effect of transformer oil on plasma ion ablation and expansion stress in large air gap between fe-based nanocrystalline ribbon and coating falls off

Fe-based nanocrystalline ribbon (FBNR) has important applications in pulse transformers. During the breakdown course, large areas of air gaps appear between FBNR and its insulated coating that falls off. In this paper, the suppression effect of transformer oil on the plasma channel expansion stress and ion ablation in the air gaps aforementioned is explored. It revealed that the "fall off" effect of coating and the physical smashing effect on the insulated coating caused by the discharge plasma expansion stress were suppressed by oil. The coating ablation and gasification caused by the discharge ion bombardment in the coating cracks mainly attributed to the coating breakdown in oil, and the coating breakdown voltage was enhanced.