Detection and Diagnosis of Broken Rotor Bar Based on the Analysis of Signals from a Variable Speed Drive

In this paper, the diagnosis of broken rotor bar (BRB) is investigated analytically and experimentally based on induction motors (IM) with variable speed drives (VSD). The analysis of the VSD process has understood that the sensorless control mode adjusts both supply voltage and current in order to maintain the operating speed within high accuracy. It means that any asymmetric problems with the rotor such as BRB will cause changes to current, voltage and power signals. Therefore, all of these signals can be used to diagnose BRB. However, experimental studies show that the components at twice slip frequency can be extracted more reliably in the spectrum of power signal which contains diagnostic information of both current and voltage signals. Consequently, it produces better results in separating different BRB cases under sensorless control mode, compared with that of using either current or voltage signal.