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Introduction

Electrical Steels (Soft Magnetic Materials) Core Losses : The energy that is dissipated in the form of heat within the core of electromagnetic devices when the core is subjected to an alternating magnetic field Electrical steel is used to multiply the magnetic flus in the cores of electromagnetic coils – transformers, electromotors, generators, electromagnets. - Highest possible permeability, and easily magnetize and demagnetize it. (a)Eddy current loss (b)Hysteresis loss

4 In order to decrease the eddy current, 1.The core can be made of an insulator 2.The core can be made from pressed iron powder whereby each powder is covered by an insulating coating. 3.Made out of thin sheets which are electrically insulated from each other

Grain Orientation Magnetic Anisotropy The magnetic properties of Crystalline ferromagnetic materials depend on the crystallographic direction in which an external field is applied Magnetization curves of single crystals If the external field is applied in the direction, saturation is achieved with the smallest possible field strength Easy Direction

Composition of Core Materials Low carbon steel : The least expensive core material is commercial low relatively small permeability, higher core losses than grain-orientd silicon iron Iron-silicon alloys : higher permeability and a lower conductivity than low carbon steel, heat treatments of these alloys can be performed at much higher temperatures with out interference from phase changes during cooling Permalloy, Supermalloy, Mumetal : The highest permeability (multicomponent nickel based alloys) Amorphous Ferromagnets - a considerably higher permeability and a lower coercivity - electrical resistivity is generally larger

Permanent Magnets (Hard Magnetic Materials) : Devices that retain their magnetic field indefinitely. Hard magnetic materials Demagnetization curve Maximum energy product

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9 Demagnetizing Curve

Magnetic Recording and Magnetic Memories

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