While official International Electrotechnical Commission (IEC) standards typically require purchase, you can find official previews and authorized guides for IEC 60072-1
: Distance between the center-lines of the mounting holes in the feet. Flange Dimensions Iec 60072-1 Pdf Free Download
"Rotating electrical machines - Dimensions and output series - Part 1: Frame numbers 56 to 400 and flange numbers 55 to 1080" iTeh Standards Official Purchase : The full document is available at the IEC Webstore Free Previews iTeh Standards : Provides a detailed PDF preview Iec 60072-1 Pdf Free Download
This standard ensures that motors from different manufacturers are physically compatible by standardizing mounting and shaft dimensions. Iec 60072-1 Pdf Free Download