Powder Magnetic Materials
Conventional metallic magnetic materials are of little value for high frequency applications for the obvious reason that they exhibit very high eddy current losses due to the conductivity of the metal. This loss is proportional to the area normal to the direction of the magnetic flux, around which the loss current circulates. Thus whilst some improvement in properties can be realised by using very thin laminations or toroidal cores wound from very thin tape, there is obviously a practical limit to the degree of subdivision obtainable. The power loss is also proportional to the square of the frequency and at power frequencies of 50 or 60 Hz laminations commonly used are of the order of 0.016 in (0.3 mm) thick. Laminations in special alloys are obtainable down to 0.004 in (0.1 mm), occasionally down to 0.002 in (0.05 mm), whilst tape cores can be wound with tape as thin as 0.0005 in (0.0125 mm). However, even at these thicknesses the loss rapidly becomes unacceptable at frequencies of the order of a few kilohertz.
KeywordsEffective Permeability Carbonyl Iron Core Loss Nickel Iron Eddy Current Loss
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