Re: Over Saturation?

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

Original poster: "Jim Lux" <jimlux-at-earthlink-dot-net> 


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Wednesday, January 28, 2004 4:15 PM
Subject: RE: Over Saturation?


 > Original poster: "Randy & Lori" <rburney6-at-comcast-dot-net>
 >
 > I knew there had to be some math in there somewhere.  So, as I
 > understand it, in most cases where I have read the term "Over Saturate",
 > they really mean that they are bringing the core out of Saturation?  If
 > voltage is increased, then current will obviously follow, and with
 > increased current comes increased magnetism, but saturation goes down?
 > I kept thing of "Saturation" as a term pertaining to magnetism; do I
 > have it backwards?  I really do appreciate the response, but until I get
 > the "Visualization", the math doesn't help.  You mentioned volt-second??

It has to do with what's called the B-H curve of the metal in the core..

Think of the core as millions of little tiny magnets that can move (like
compass needles) and are on little springs.  You put an external field on
it, and some of the magnets start to align with the external field.  More
field, more little magnets align. Up until ALL of the magnets are aligned,
then, putting more external field does nothing.... You've saturated.

With, so called soft materials (iron, transformer laminations, etc) when you
remove the external field, the little magnetic domains all relax back to
where they were before.
With "hard materials", once you've made the domain point a particular
direction, they tend to stay that direction (making a permanent magnet)
until you put a different field that's strong enough to "break them loose"
or unstick them.  The field required to do this is called the "coercivity"

Yet another factor is how fast the magnetic domains can set or turn.  If you
put a changing field on the material, the little domains have to spin back
and forth on every change in the field.  There's some frictional losses in
this process (core or iron losses in a transformer) and it also why there's
a frequency limit on some materials.