Effect of tension and surface properties on magnetic domains and power loss in amorphous ribbons

Tez Türü: Doktora

Tezin Yürütüldüğü Kurum: University of Wales College of Cardiff, Enginering Faculty, Electrical Electronic Engineering, Birleşik Krallık

Tez Danışmanı: Turgut Meydan

Tezin Onay Tarihi: 1994

Tezin Dili: İngilizce

Desteklendiği Program: Diğer

Özet:

Energy losses in electrical machine cores cause a great world-wide demand for a cheap low loss core material. Silicon-iron has traditionally been used as a core material, however, amorphous materials offer a significant potential energy saving in electrical machine cores due to the their superior magnetic and mechanical properties.

The understanding of the causes of energy loss have been greatly related to domain structure in the material. Hence, domain observations were performed on commercially available amorphous ribbons using the Kerr effect.

Amorphous ribbons usually have an irregular leaf domain pattern in the unstressed state. However, domains gradually transform into a system of antiparallel longitudinal domains along the ribbon length under tension. So, the meaningful domain wall spacing measurement can be carried out under the combination of tensile stress and controlled magnetisation.

These observations showed that domain wall bowing occurs in amorphous ribbons. The degree of bowing was reduced with increasing frequency and varied with surface polishing and tension. It is attributed to the structural inhomogenity across the ribbon thickness. The domain observations also showed the domain wall may have a complex shape in the ribbon.

Loss measurements were also made by using the initial rate of rise of temperature method and were correlated with the findings of domain observations. The loss measurements verified the inhomogenity in the ribbon. The energy saving was maximum if the inhomogenity was reduced by polishing both surfaces.

The chemical elements in the ribbon have different concentration across the thickness. The element concentration is more uniform in the middle than near surfaces of the ribbon.

The investigation, hence, verified the importance of the homogeneity in amorphous ribbons which causes a non-sinusoidal, non-repetitive and non-uniform domain wall motion which is the cause of high anomalous loss. If it is improved the energy loss may significantly be reduced.