Magnetic properties of Alcomax III with dynamic excitation

The distribution of B and H in a solid specimen of Alcomax III with sinusoidal surface field, at frequencies of 50¿350 Hz, is calculated by a numerical solution of the field equation. The reduction of internal hysteresis effect owing to flux inhibition, caused by eddy currents, is considered using a nest of minor static B/H loops. Eddy-current density, eddy-current loss, hysteresis loss and total-energy loss per unit volume are predicted, using finite difference equations. The energy loss per unit volume of a specimen of Alcomax III was accurately measured for sinusoidal field in the frequency-range region 50¿350 Hz by measurement of the areas under dynamic B/H loops. This loss agreed with a direct wattmeter method and also with the theoretical field method. Eddy-current loss was negligible at 50 Hz, and, even at 350 Hz, constituted only about 10% of total loss. Total loss was found to be almost a linear function of frequency at fixed field intensity.