Using current signature analysis technology to reliably detect cage winding defects in squirrel cage induction motors

This paper demonstrates, through industrial case histories, the application of current signature analysis (CSA) technology to reliably diagnose rotor winding problems in squirrel cage motors. Many traditional CSA methods result in false alarms and/or misdiagnosis of healthy machines due to the presence of current components in the broken cage winding frequency domain that are not the result of such defects. Such components can result from operating conditions and drive components such as mechanical load fluctuations, speed reducing gearboxes, etc. Due to theoretical advancements it is now possible to predict many of these current components, thus making CSA testing less error prone and therefore a much more reliable technology. Reliable detection of the inception of broken cage winding problems, or broken rotor bars, prior to failure allows for remedial actions to be taken to avoid significant costs associated with consequential motor component damage and unplanned down time associated with such in-service failures.