Re: Over Saturation?

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

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

Hi,
     Flux density is in Teslas, freqency in Hz, area in M squared.We
usually design for about 1.2 T peak flux density for 1 off's, or 1.6 for
toriodial cores. You can go higher but your design needs to be done
carefully then. Ferrites at about 20KHz I usually run at about 0.2 T,
dropping to about 0.1 at 150 KHz Most power ferrites saturate at about
.385 T.
     I once visited a friend who was manufacturing battery chargers and
noticed an output choke with no gap, so told him to take the core out
and save some money as it was not doing anything. He eventually replaced
it with a resistor and had no change in performance.

George
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, January 29, 2004 5:02 PM
Subject: Re: Over Saturation?


 > Original poster: Ed Phillips <evp-at-pacbell-dot-net>
 >
 > "Not too much of a reflection on you, any people involved in
electronic
 > design don't understand this one either! Often people ask "how much
can
 > I load it before it will will saturate?" or something similar, but
 > increasing the load actually moves a transformer further from
 > saturation. Increasing the supply voltage or reducing the frequency
 > causes saturation as it is the volt-second product that is the
critical
 > issue.
 >
 > The formula n/v =1/ 4.44BFA tells you what the flux density is.(B)
 >
 > F= frequecy
 > a= Area of the core in Metres
 > n/v = turns per volt
 >
 > George Tyler"
 >
 > Very timely note.  A few questions:
 >
 > Do you mean area in meters^2?  (This is the US, hence the meters but
 > they are all the same of course.)
 >
 > Flux density in gauss or Tesla?  I'm used to using core area in cm^2
 > and gauss (I'm an old timer) and haven't tried conversion of your
 > formula.
 >
 > Final point is you should include the allowable flux densities for
good
 > transformer "iron" and also for typical ferrite core materials.  see a
 > lot of reports here of guys winding NST protection "chokes" by
wrapping
 > a few turns of wire around a loop core or something like that.
Doesn't
 > take much calculation to see that the core isn't doing anything.
 >
 > Ed
 >
 >
 >