Application of statistical tools to the investigation of coil failures

The investigation of failure mechanisms in stator coils is considered an art and can consume a significant amount of time and valuable resources. The authors have applied rigorous experimental methodology and statistical principles in the investigation of hi-pot failures, analysis of voltage endurance test results and other insulation projects. Application of statistical tools has been found to increase the efficiency of the work and increase confidence in the conclusions. This paper discusses the investigative methods using examples such as failure modes and effects analysis, hypothesis testing, design of experiments and analysis of variance. The discovery of potential areas of process improvement based on voltage endurance testing of one insulation system is discussed.