Electrical Aging of the Insulation of Low-Voltage Machines: Model Definition and Test With the Design of Experiments

The aim of this paper is to present a method for modeling the life span of insulation materials in a partial discharge regime. Based on the design of experiments, it has many advantages: It reduces the number of time-consuming experiments, increases the accuracy of the results, and allows life span modeling under various stress conditions, including coupling effects between the factors. Accelerated aging tests are carried out to determine the life span of these materials. The resulting model presents an original relationship between the logarithm of the insulation life span and that of electrically applied stress and an exponential form of the temperature. Results show that the most influential factors can be identified according to their effects on the insulation life span. Moreover, the life span model validity is tested either with additional points which have not been used for modeling or through statistical tests. Finally, it is shown that fractional plans are not suitable to reduce the number of experiments. This application of the experimental design is best used during the initial phase, before the final drive has been built and any online diagnosis.