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(Last updated: 04-Apr-2018 19:25 )

About Amorphous cores

Amorphous material looks and feels like metal, and is of course magnetic too. Yet it is not a metal, but an alloy of metal and glass. Wheras metal always crystallizes after cooling down from melting, glass will not crystallize, but is more like a very thick fluid. It is possible to melt metal and glass and mix this, approximately 1:1 When cooled down, the "alloy" will become what is called amorphous, translated as "shapeless". The refers to the microscopic picture. With metal, the crystals can be made visible, with photographic methods, and they form patterns. Fir this, think about the "sand" structure you may have seen when solder is cooling down, and you wait not long enough. These are the metal crystals. With glass + metal mixture, it becomes neither of the two. There are no crystals, but a much finer, structure of no particular shape. So the elementary magnets are smaller, and also the remanent magnetism is very very low. Meaning the "BH" curve is much nicer shaped, more ideal, but of course maximum saturation is lower, because half of it is glass.

Amorphous alloys ribbons are produced by rapid  solidification of  melted metals at very fast cooling rate. The makes the alloy solid before the atoms have a chance to crystallize. (WIth pure metal this will not work. You can influence the crystal shape by very fast cooling, like when hardening steel that way, but you can not prevent crystallization). WIth Amorphous material, you can prevent crystallization, and create very beautiful BH curves that way. Wheras BH curves of pure metal are never as nice as amorphous. A wide variety of  amorphous alloys is available to meet the wide  range of needs of transformer designers.

 

    General properties of Amorphous Alloy Tape

    • High permeability and low coercive force
    • Low core loss and low exciting power
    • Good temperature stability (working temperature -50°C ~ +130°C)
Typical applications of Iron Based Amorphous Alloy Tape:
    • Smooth current wave filters and PFC inductors
    • Differential inductors in switch-model power supply
    • Video and audio application.
    • Single phase and three phase transformer cores
    • Power switch transformer cores

    Typical applications of Cobalt Based Amorphous Alloy Tape:

    • Magnetic amplifiers, noise suppressors, pulse transformer cores
    • Differential inductors in switch-model power supply and common mode cores
    • Transformer cores of high frequency power switch (30kHz~200kHz)
    • Output filters and energy inductors

    Disadvantages:

    • expensive
    • very hard material
    • gives sharp particles during production

    Two approaches to Amorphous cores

    1) The  technical approach.  For that you need to know and understand what the hysteresis of a transformer material is doing to the signal transfer.  This is the higher permeability, lower coercive force, low core loss and low exciting power.  Also the shape of the hysteresis curve is more linear,  more square shaped.   This gives a complex mix of new electrical parameters to amorphous cores,  compared to normal steel cores.  

    2) The listener's approach.  Decide for yourself what sound you prefer.  With today's modern core materials,  amorphous cores are appreciated by "connaisseurs" of tube sound. Before that,  there was already the use of this material for some high end moving coils transformers.       Theoretically Amorphous material has a fraction higher distortion, but practically the sound is preferred by many.     Most comments are like this:

    • more realistic sound picture
    • more natural sound
    • less listening to "the transformer"

    Whatever approach may be right,  for sure is, that despite the higher price,  there is a fast, very fast  growing interest in these products! 



    © COPYRIGHT NOTICE All Rights Reserved


    (Last updated: 04-Apr-2018 19:25 )