Aging under AC voltage of polyurethane by using Weibull statistic

The electrical aging of polyurethane under AC voltage has been investigated. This material is used as insulating material in the electrical machines. A Weibull statistical analysis of the time to breakdown was performed. The study shows that the V-t characteristic of the polymer includes three zones. The first one corresponds to the defects of youth. The second represents a statistical dispersion of the intrinsic defects of the material. The third expresses the real aging of the polymer which changes. The slope variation of the V-t curve is related to the change of the degradation mechanism. This degradation is governed by the action of the partial discharges.