Over Saturation

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

Original poster: "Philip Chalk" <phil-at-apsecurity-dot-com.au> 

Randy & Lori, et al.

Don’t know if this helps……….

Maybe I've missed or am misunderstanding something, but I, for one have a 
bit of a semantics problem with the term 'over saturate'.  My memory's 
getting worse & worse, & I’m no transformer expert, but I've been in & 
around electronics for a long time & don't recall ever having heard the 
term used before.  'Saturate', sure, but not 'over saturate'.  It's a bit 
like 'over-exaggerate'.  It's either saturated or it's not (except maybe 
over a small transition region where it might be not well defined). You 
can't really be 'a lot saturated'. Perhaps it might be taken to mean, for 
instance, '(input voltage or current)beyond the point of saturation' ?

On a mains transformer, say, with the secondary open, you wind the primary 
voltage up & the (magnetizing) current increases roughly linearly with the 
voltage till the saturation 'point' is reached.  Then the current rises 
abruptly, and increases a lot(exponentially) for even small increases in 
voltage. So the output waveform distorts & produces harmonics; the thing 
will probably hum & buzz & grunt, or otherwise complain, get hot, smoke, 
blow fuses & other stuff you don't want.

Then it is saturated.  Double, triple the input voltage now (or halve the 
frequency)& it's only a tiny bit more saturated, if at all (or measurable). 
It can’t become more saturated; the iron is carrying as much flux as it is 
able to. (Sure it’ll draw more current, dissipate more power as heat, smoke 
faster, etc, but magnetically it’s no (not much) more 
saturated.(fundamentally, it has to do with orientation of magnetic domains 
in the core material, so I suppose there is a theoretical absolute 
saturation point where every single one of them is aligned.)

I don’t even know (someone will – pls tell me.) if there is any ‘formal’ 
definition (like is, say, for a rise-time)of where the saturation point 
occurs  – it seems usually to be described qualitatively. Maybe it could be 
when the input current reaches twice the rated magnetizing current, or 
something ?

And having said that, like a zener voltage, or a boiling point, or most 
anything, it doesn't actually happen ‘at a point', it happens over a curve 
- it depends a bit on what scale you're looking at it.  In practice though, 
it appears to happen pretty suddenly.

Anyway, having taken this long to say that little, I’m too wordy to go on 
about the mechanics of it in depth (and there are far better authorities 
than me around here, anyway), so I found a couple of things which will 
probably help you understand.  Have a look here :-


http://www.oz-dot-net/~coilgun/theory/saturation.htm

http://www.allaboutcircuits-dot-com/vol_2/chpt_9/1.html
(this one was good, with some graphs, but now does’nt work, might when you try)

http://www.clarkson.edu/~ortmeyer/spt.doc


Cheers,

Phil Chalk.










-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Thursday, 29 January 2004 5:35 PM
To: tesla-at-pupman-dot-com
Subject: Re: Over Saturation?

Original poster: "gtyler" <gtyler-at-drummond-dot-org.za>

Flux density goes up with increased voltage, but the series resistance
of the primary means that as you increase the load on the secondary the
voltage across the actual primary decreases causing a drop in flux
density. You really need to draw the equivalent cct to see what happens,
but it takes me ages to draw circuits in emails and I have to go fight
with the taxman today!

George


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, January 29, 2004 2:15 AM
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??
  >
  > Randy
  > Savannah, GA
  >
  > -----Original Message-----
  > From: Tesla list [mailto:tesla-at-pupman-dot-com]
  > Sent: Wednesday, January 28, 2004 10:11 AM
  > To: tesla-at-pupman-dot-com
 >   >
  >   >  > Original poster: "Randy & Lori" <rburney6-at-comcast-dot-net>
  >   >  >
  >   >  > Can someone explain Saturation and Over Saturation as it
pertains
  > to
  >   >  > Transformers and Inductors?  I know the term and I have a clue,
  > but
  > how do
  >   >  > you know?  Why does my Variac (powered up) give me 0 volts
  > difference of
  >   >  > potential when an ohm meter tells me 0 ohms?  I don't need a
  > lesson
  > on how
  >   >  > my meter reads in DC, I know it's the AC but how?  I even
taught
  > Basic
  >   >  > electronics for three years in the military, but this one has
  > always
  >   > eluded me.
  >   >  >
  >   >  > Randy
  >   >  > Savannah, GA
  >   >  >
  >   >  >
  >   >
  >   >
  >   >
  >
  >
  >