Iron losses in induction motor teeth

Waveforms of the flux densities occurring in the stator and rotor teeth of a 700 hp squirrel cage induction motor were measured for various stator voltage and load conditions. Harmonic analyses were made of these waveforms and the determined harmonic values were compared with the designer´s predicted harmonic content. In addition, iron loss measurements determined using the Epstein test method were made on several materials using the same flux variations as existed in the stator and rotor teeth, Losses in the stator teeth were found to be as much as 100% greater, depending on the material being used and the induction level, than the losses measured using a pure 60 Hz sinusoidal flux variation with the same maximum induction. Losses in the rotor teeth were less than 0.1 watt/pound indicating little loss in the rotor teeth (neglecting rotor surfaces losses).