SEW Eurodrive calculated how the losses for aluminum and copper rotors were distributed. Use of copper-rotor bars and additional lamination stack material cut rotor energy losses as well as stray load losses. SEW says this is due to lower slip of the aluminum-rotor motor. Use of a better grade of electrical steel also reduces the iron losses by nearly one third despite somewhat higher air-gap flux densities in the copper-rotor motors. Lower rotor, iron, and stray-load losses reduce winding temperature and, thus, stator-copper losses. The efficiencies can be maintained over a wide range of loads.