RE: Finding 'mu' for magnetics

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Mccauley, Daniel H" <daniel.h.mccauley-at-lmco-dot-com> 



mu = L/Lo where L = inductance of coil on core and Lo is inductance of
coil using air as the core.
This will give you an initial "real" part of the permeability and may be
okay for what you are doing.

However, amplitude-type permeability is a more important parameter and
is not so easily obtainable.  Basically
this is determining the B-H curve of the core and is one of the most
important characteristics of the core when
doing a design.  Much more than initial permeability.

Dan


 > Hi All
 >
 > For those of us who are saving the planet by using re-cycled
 > materials for
 > our coils and apparatus, I have been wondering how we can
 > determine the
 > factor 'mu'
 > for ferrites and other materials that go into gate drive
 > transformers,
 > flyback transformers, etc.
 >
 > My proposed method:
 >
 > 1) Wind a coil on the core, measure the inductance.
 > 2) Take coil of core, measure inductance again.
 > 3) Calculate mu from ratio.
 >
 > Sounds too simple - but is it?
 >
 > Cheers
 >
 > M
 >
 > --
 > Matthew Smith
 > Kadina Business Consultancy
 > South Australia
 > http://www.kbc-dot-net.au
 >
 >
 >