Impedance sweep frequency response analysis for the in-situ inspection of distributed stator windings in induction motors

Impedance sweep frequency response analysis (SFRA) offers significant advantages as a non-destructive testing technique both for the ex-situ and in-situ inspection of rotating electrical machines and machine components. The diagnosis of squirrel cage induction motors (SCIMs) with random-wound stator windings via SFRA poses significant challenges due to the highly variable conductor positioning within the stator slots. This, combined with their widespread use in various industrial and transportation applications, has induced significant research attention on the application of SFRA to SCIMs. This work presents an extensive application of winding inspection using impedance spectroscopy measurements, in which a population of 22 SCIM specimens are tested via SFRA, where the variability of the machines' distributed winding is observable. Additionally, two different representation methods (i.e., bode and Nyquist impedance plots) are utilised to elucidate defective SCIMs using impedance spectroscopy as means of in-situ inspection.