Case study on the effectiveness of gear fault diagnosis technique for gear tooth defects under fluctuating speed

Gears are very reliable parts of wind turbines and normally contribute for more than 5 years without failure when operated under fluctuating speed conditions. This case study presents the effectiveness of gear fault diagnosis techniques to highlight cracked tooth, chipped tooth and missing tooth gear under fluctuating speed conditions. Various measuring parameters such as overall vibration acceleration and envelope-detected acceleration were calculated for vibration signal, and sound intensity and sound pressure were calculated for acoustic signal. A statistical indicator kurtosis was also calculated for both vibration signal and acoustic signal. These measuring parameters were then compared with showing the fault detection capability of techniques employed under fluctuating speed and also under different loading conditions. The detection of faults by kurtosis of acoustic signal is found most efficient. For low load conditions, envelope-detected acceleration of vibration signal can also support fault diagnosis under fluctuating speed conditions.