Reliability quantification of induction motors-accelerated degradation testing approach

Characterizing life of cheap, highly reliable devices, such as small induction motors, is a challenge due to cost and time restriction. Accelerated degradation testing (ADT) provides a way to predict its life cost- and time-effectively. Having time tracking on degradation signals within relatively short test duration, the reliability can be estimated through accelerated degradation testing, even without any failures. ADT on induction motors have been conducted in the GE R&D Center to quantify the motor reliability. A new degradation index, the Orbit Area, for the induction motors is proposed, which turns out to be one of the most reliable indices for time tracking motor bearing wear. Signal processing method for extracting this degradation index from measured signals was developed. A time-to-degradation model is constructed based on the physics of failure and test observations. Maximum likelihood estimation is employed to analyze test data. The reliability of the motors is finally predicted through the obtained degradation model. Several issues regarding ADT and lessons learned are also discussed in the paper.