Motor Health Monitoring at Standstill Through Impedance Analysis

Induction motors are the most common driving force for active mechanical components such as pumps and valves. When these motors are used in safety systems, which are normally on standby, monitoring the motors through nondestructive evaluation techniques is needed to guarantee their operability and system integrity. In this context, this study suggests a method for motor health monitoring at standstill through impedance analysis. Impedance change tendencies for various motor failure cases are investigated. To identify the tendencies, first an equivalent circuit (EC) of an induction motor is developed, and probable impedance changes for each failure case are estimated based on the developed EC. Then, the estimates are experimentally verified by reproducing the failures and measuring the impedance with an impedance analyzer. As the equivalence between the estimates and the experimental results is confirmed, unique tendencies in impedance changes for each failure case are characterized. The suggested method is expected to be useful in areas with access restriction, such as nuclear power plants (NPPs), as motor impedance can be measured from a distance without any disruption on-site.