Condition monitoring of shaft of single-phase induction motor using optical sensor

Transmission type of optical technique is developed to sense the condition of rotating shafts from a distance. A parallel laser beam is passed tangential over the surface of rotating shaft of a single phase induction motor and its flickering shadow is received on a photo sensor. Variations in sensor voltage output are observed on a digital storage oscilloscope. It is demonstrated that this signal carries information about shaft defects like miss alignment, play and impacts in bearings along with surface deformities. Mathematical model of signals corresponding to these shaft defects is developed. During the development and testing of the sensor, effects of reflections are investigated, sensing phenomenon is simulated, frequency response of the sensor is obtained and its performance is compared with conventional accelerometer.

► The sensor developed gives a unique access to rotating shaft condition monitoring.
► Reflection properties of different shaft surfaces do not affect the results much.
► Results from accelerometer and optical sensor show almost complete correlation.
► The signal generated reveals the information about various shaft defects.
► The impacts of the shaft on bearings clearly appear if present.