Efficiency assessment of induction motors operating under different fault conditions

Fault diagnosis in induction motors has been a topic that has drawn an increasing attention among the electrical engineering community, including both industry and academia. Diverse techniques have been developed in order to detect the presence of possible faults in their early stages, so that forced outages of the motor and consequent economic consequences can be avoided. However, little attention has been paid to the implications of the presence of these faults in terms of motor efficiency reduction. The efficiency drops caused by the existence of faults or anomalies in the motor, which can be present during long time intervals, can lead to economic losses that can be even greater than those caused by eventual motor outages. In spite of this fact, many industrial users are not aware of the efficiency repercussions of the operation under non-healthy conditions. As a consequence, it becomes necessary to accurately study and quantify the efficiency decrements caused by the presence of possible failures, so that the users can have this information available to adopt proper maintenance decisions. This paper analyses how different failures influence the value of motor efficiency; diverse types of rotor faults as well as bearing failures are considered. It is shown how the presence of these failures affects the motor efficiency and may have serious implications on the motor performance.