Measurement of the magnetisation characteristics of high-permeability magnetic sheet steel

An investigation has been carried out into the problems of measurement of the initial permeability curves and hysteresis ioops of samples of high-permeability sheet steel, particularly oriented 3% silicon iron. Experiments were carried out to determine the variation of permeability from point to point in a sheet, the uniformity of flux in samples under test, and the errors in ballistic galvanometers due to prolonged impulses. A new precision permeameter was constructed, particular features being a fluxgate magnetometer, to ensure correct compensation, and pushbutton-controlled relays, for switching the magnetisation and compensation currents. A quantitative analysis of the m.m.f. required for compensation is made, and the need for correct compensation for all measurements in such a permeameter is demonstrated.