Analysis of 3D Computed Tomographic Imaging of Ground-wall Insulation for AC Rotating Machines

The X-ray Computed Tomography (X-CT) has been used to reconstruct the internal features of two types of ground-wall insulation for ac rotating machines. Four samples whose insulation was designed for a rated voltage of 11 kV, were extracted from different coils and scanned using X-CT. The 3D virtual volumes have been visually inspected stacking the tomographic slices to identify the internal morphological features that is, the different materials in the inner structure, the presence of minute voids, gas bubbles, anomalous densities, wrinkled or damaged tape layers. The tomographic volumes have been segmented into different gray-levels resorting to luminosity histograms with the purpose to differentiate the structural materials and extract only specific anomalies. In particular, the binary segmentation has been adopted to investigate the distributions of the void enclosures. The use of X-CT to investigate the internal structure of complex insulation systems, opens significant perspectives in improving the insulation manufacturing quality.