Measurement of iron losses in magnetic sheet steel subjected to a high alternating magnetic field

Two sets of apparatus, one at Manchester the other at Sheffield, designed to measure iron losses in sheet-steel samples magnetised at high flux densities, are described. The measurements were carried out in each case by a different thermal method. Many of the difficulties common to all thermal measurements were present, and errors were only reduced by careful techniques and attention to detail. Two different methods, one electronic and the other dynamo-electric, of producing a sine wave of flux density at the required very high values were also developed and are described. Measurements have been made of the loss in several grades of silicon iron, with sinusoidal flux waveshapes up to flux densities of 22.5-24 kGs, according to the type of steel. The two different experimental systems have yielded answers in good agreement. Experiments are described which show that, for the materials tested, the loss directly proportional to frequency (hysteresis) reaches a saturation value at high flux density. Measurements of anomaly factor have been made, and some indication is also given of the way in which the total loss varies with form factor.