Class E.646 did not follow the standard Italian class numbering rules where the last digit indicates the number of motors, as it mounted 12 two by two mechanically coupled 82-333FS type electric motors, each providing , fed from the 3000 V catenary. These motors were more powerful than those mounted on the predecessor E.636 class and able to improve performance up to 50% with only a 20% increase in weight; this also increased the mass available for adhesion, giving it better hauling ability.