End-winding vibration monitoring and interpretation

Over the last two decades, the end-winding vibration monitoring of large generators and motors has been rendered possible by various methods. This paper focuses on our experiences with nonconductive and nonmetallic fiber optic accelerometers. Over 2000 of these accelerometers have been installed in the field on various types and sizes of large rotating machines. Data obtained from the accelerometer under different operating conditions and their interpretation have provided reliable information and valuable knowledge to establish guidelines for acceptable levels of end-winding vibration. But proper interpretation also requires identification of the frequencies where each vibration occurs. The combined effects of amplitude, conversion of acceleration to displacement as a function of frequencies of the vibration, represent the true method to evaluate the level of stiffness of the end-winding system.