Magnetic properties of grain-oriented silicon iron. Part 2: Basic experiments on the nature of the anomalous loss using an individual grain

Abstract

SynopsisMeasurements of the position of the parallel-bar-domain walls at various points on the magnetising cycle have been made over the frequency range 25-100Hz in an individual grain of transformer steel, using the Kerr magneto-optic technique.A single-turn search coil of very thin wire wound around the test grain, through two 0-004 in holes, enabled the flux density to be measured. By plotting the degree of magnetic saturation, as indicated by the position of the surface walls, against the degree of saturation, as measured in the volume by the search coil, the amount of domain-wall bowing could be noted at various frequencies. Even at 25 Hz, there exists considerable bowing.In addition, the total power loss in the same grain has been measured at various flux densities in the frequency range 10-100Hz, using the rate-of-temperature-rise technique reported earlier.The importance of carrying out this basic study on a single grain is noted, and the experimental results are discussed in terms of various domain models, and of the various concepts that have been introduced to explain the nature of the anomalous loss.

Anisotropy in Some Soft Magnetic Materials

“…These are believed to derive from transition band and grain boundary nucleation sites respectively, and will be considered in detail elsewhere. 19.20 The orientation distribution for the silicon iron ( Figure 6) is similar to the rimming steel (Figure 4) (5) where the average is carried out over a sufficiently large volume of orientation space. This approach has been outlined by Bunge 13 in relation to texture description using spherical functions.…”

The analysis of eddy-current-limited magnetic domain wall motion, including severe bowing and merging

“…By distributing the flux reversal over a greater area, and weighting it in favour of more superficial regions, domain wall bowing leads to a considerable reduction in eddy current drag. Bowing has been reported by a number of authors (eg Boon and Robey 1968, Overshott et al 1968, Helmiss 1969) even in silicon-iron, which has a higher domain wall surface…”