Thermal Degradation Profile Mapping in Stator Coil Insulation by Impedance Spectroscopy

Impedance spectroscopy is one of the continuously developing tools deployed for the inspection and evaluation of the health condition of electrical machines and machine components. Being a practical implementation and expansion of the Broadband Dielectric Spectroscopy (BDS) and the Electrochemical Impedance Spectroscopy (EIS), it allows the characterization of components by their amplitude and phase responses over frequency and the system's resonances. To this direction, this paper presents a study on the effect of thermal degradation on the insulation system of concentrated stator coils from the stator winding of a 2 MW permanent magnet synchronous generator purposed for aerospace applications. The thermal aging pattern and degradation mechanisms of the coil insulation are discussed through experimental results by ex-situ impedance spectroscopy.