While comparison of the torque produced by AC machines of a given topology is, today, a standard feature of the machine design process, comparison of machines from different families of machine types is less frequently undertaken. This two part paper compares the torque performance of 6 types of AC machines based on the same current level, flux level and rotor dimensions. A new “tau” factor is introduced as means for comparison of any AC machine with an “ideal” machine based upon Essesn's Equation.