ShamsMosavi S., Poshtan J., Zarei J.

One of the main induction motor defects is a broken rotor bar. There are two approaches to the diagnosis of this defect. In the first approach, the Condition Monitoring of the motor is achieved based on the comparison of signals from the defect motor and the healthy motor. While in the second approach, the fault detection should be carried out without any a priori signals from healthy motor. So far, the main research on fault diagnosis of induction motors has been with the aim of Condition Monitoring. It should be mentioned however that not as much research is available to determine a threshold for making decision about the motor health without having a priori knowledge of the motor. In this paper some formula has been extended for determining a threshold in the well-known park's vector and instantaneous power analysis, as well as for the motor current analysis. It has been shown that the threshold in the park's vector and instantaneous power analysis is not as effective as the same threshold at the motor current analysis. Also, it has been illustrated that how the improper motor loading can make negative effect on the above-mentioned threshold, while a virtual loading can improve the results.