Working out resistance of reluctance

Discussion in 'General Electronics Chat' started by nigelwright7557, Feb 4, 2014.

  1. nigelwright7557

    Thread Starter Senior Member

    May 10, 2008
    487
    71
    I am using an ET54 core with a 0.5 mm gap.

    Does anyone know the reluctance of this gap ?
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,788
    945
    I could not find any reference material specific to that core size that did not also mention core material and winding method with freq of interest.

    I did find a good paper with many formula and design suggestions. Perhaps it could clear up some questions you may have or otherwise be helpful.

    http://www.ieee.li/pdf/viewgraphs/fundamentals_of_magnetics_design.pdf
     
    nigelwright7557 likes this.
  3. nigelwright7557

    Thread Starter Senior Member

    May 10, 2008
    487
    71
    I eventually found this but my maths is wrong somewhere.


    l/ uo * ur * A

    l=0.0005 metres (0.5mm gap)
    uo = 4 pi 10power-7
    ur = 1610 for 3c90 core
    A = 0.00028metres squared

    This gives 882.6 which is nonsense.

    I did a search of the internet and someone was getting 1 ohm for a 1.5mm gap.
     
  4. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    Reluctance is the relationship between magnetic flux and mmf. Nothing to do with ohms. Although some people find the electrical analog helpful.

    I suggest you review your understanding of magnetic circuits.

    Perhaps this might help

    http://www.allaboutcircuits.com/worksheets/magnet2.html

    Looking at the equation should show you that gap length isn't the sole determinant of reluctance.

    An air gap has a relative permeability of 1 - not 1610. So it's even "worse" than you envisaged.
     
    Last edited: Feb 5, 2014
  5. vrainom

    Member

    Sep 8, 2011
    109
    19
    Last edited: Feb 6, 2014
Loading...