Evaluation of Faults in the Squirrel Cage Three-Phase Induction Motors

Abstract

Induction motors have played a central role in the techno-economic development of modern industries and electric power generation. However, the presence of recurring failures hinders a cost-effective performance and leads to catastrophic damage. Therefore, the present study proposed an assessment to investigate the influence of two types of failures in induction motors, namely failure due to broken bars in the rotor and defects in the connection between the rotor bars and the end ring. Accordingly, a three-phase induction motor was evaluated under different failure conditions that modified the operational torque and rotational speed. The results indicated that both types of failures magnify both the core and copper power losses by up to 13.3 % and 8 %, respectively, compared to the healthy condition. On the other hand, an efficiency reductionbetween 1.94 % to 3.41 % is an indication of failure progression. Finally, the appearance of harmonics 3 and 7, and the intensified magnitude of harmonic 5, represent a clear sign of failure occurrence related to rotor barsand defects in the connection to the end ring. In conclusion, the proposed methodology proved to be an adequate tool to predict failure appearance, which has a direct impact on extending the lifetime of induction motors.