Iron Loss Measurements of Non-Oriented Electrical Steels at Elevated Magnetic Polarization: Comparison of Calorimetric and Field-Metric Methods

The tendency to increase the magnetization levels in parts of the rotating electric machines leads to relevant requests for appropriate magnetic data of non-oriented electrical steels, including magnetic iron loss curves at more elevated magnetic polarizations than what is classically feasible. Indeed, for the most commonly used field-metric or watt-meter methodology, it is understood that at elevated magnetic polarization amplitudes (typically J > 1.7T), the iron loss measurement accuracy is highly impacted by any small parasitic phase shift fluctuation between magnetic field and induced voltage. This parasitic effect at elevated J results in an absolute error ε <; 0 on the field-metrically measured losses (meaning that at elevated J, the iron losses are typically underestimated by the field-metric method). To overcome this constraint, the calorimetric method is a valid alternative to measure iron losses at elevated J. In this paper the calorimetric methodology is applied on an Epstein frame configuration, with the objective to merge both the field-metric losses and the calorimetric losses into an extended loss data sheet for nonoriented electrical steel grades, to better serve the electrical motor and generator designers, particularly for the traction machine development with the iCARe® range of electrical steel grades which are optimized for automotive applications.