Motor guidance: Effects of post-repair testing on inductance

Inductance measurements are often used for trending, troubleshooting and quality control testing of motor health. Once a motor is installed and running under the normal operating conditions of its parent application, an expected range of inductance can be acquired and used as a comparison to easily identify changes in the motor health.

Using inductance values for quality control or acceptance testing doesn't always offer the luxury of comparison data or running history as the motor has not been installed into an application. Instead, the motor has only the magnetic image or memory of the last test performed during and after the motor repair. If the last test performed post repair is a single-phase test on a three-phase motor, the remaining magnetic image on the motor will represent a magnetic anomaly. Just as it should if you tested a three-phase motor in the field that was secured after a single-phase fault in the power supply. 

For more information on electric motor reliability, visit www.pdma.com.