Online detection of endwinding contamination in industrial motors

This paper discusses a novel online technique to detect moisture and surface tracking of stator end-winding insulation in medium/high voltage AC motors. A novel high sensitivity differential current transformer is used as a sensor for monitoring insulation capacitance and dissipation factor of motors online. A 100 hp, 4160V, 3-phase form-wound induction motor is tested with different contaminants sprayed on its end winding. Partial discharge couplers are also used to monitor partial discharge activity during insulation contamination tests. A comparison of both techniques to detect pre-cursors of motor failure due to end-winding tracking is presented in this paper.