Iron loss in non-oriented electrical steels under distorted flux conditions

When developing new non-oriented electrical steels and assessing their performance in electrical machines their properties when magnetised under nonsinusoidal flux conditions must be considered. Several methods of approach have been attempted in the past but in this paper the performance of single strips has been examined in a purpose built computer controlled magnetising and loss measuring system. A range of non-oriented materials were tested and their losses were generally found to increase by around 10% with a 15% 3rd harmonic content in the magnetising waveform. The phase of the flux density harmonic relative to the fundamental was found to be important and its neglect caused loss prediction errors of up to 20%. The loss of the non-oriented steels did not increase so rapidly under distorted flux conditions as in grain oriented steels and in general materials with lower nominal losses had higher deterioration factors.