The X-ray computed tomography has been applied here to inspect the internal features of two types of ground-wall insulation systems of ac rotating machines. Samples extracted from complete coils were scanned and their internal structure was analyzed by means of virtual slicing and 3D rendering procedures. Specialized software tools have been used to discover the morphological features of both the distributed voids and the high-density anomalies. It is was found that the resin penetration as well as the density and the geometries of the distributed micro-voids depend from the tape characteristics.
