AC Electrical Breakdown Characteristics of an Epoxy/Mica Composite

Epoxy/mica composite was synthesized, in order to use it as an impregnation resin in a vacuum pressureimpregnation (VPI) process, for manufacturing a high voltage rotary machine. The average particle size of the micawas 5~7 μm and its content was 0, 20, 30 and 40 wt%. A plasticizer or a low molecular aliphatic epoxy was also used,to decrease the viscosity of the composite. The AC electrical breakdown strength was estimated in sphere-to-sphereelectrodes, and the electrical breakdown data were estimated by Weibull statistical analysis. The electrical breakdownstrength became higher with the addition of mica; and that of the system with 20 wt% mica was highest. The electricalbreakdown strength of the system with an aliphatic epoxy was higher than that of the system with a plasticizer.