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
    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
    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.
    nigelwright7557 likes this.
  3. nigelwright7557

    Thread Starter Senior Member

    May 10, 2008
    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
    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

    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


    Sep 8, 2011
    Last edited: Feb 6, 2014