Re: Rebuilding an OBIT

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

Original poster: "Luc by way of Terry Fritz <twftesla-at-uswest-dot-net>" <ludev-at-videotron.ca>

Hi Ed

May be I make a mistake but the formula I have for the numbers of turns  in
a primary of a
transformer is different.
My formula is:  N = (E · 10^8)/ (4.44·f·A·B), where N=Number of turns;
E=Primary Voltage;
       f=line-frequency; A=core cross-section Area; and, B=max.flux, in
lines. Assuming 60,000
lines of flux...
or N = (k·E)/ A, where k=6.256 when f=60 Hz., or, k=7.507 if f=50 Hz.

My formula could be no good, I never wound a transformer myself but on a 2
square inch cross
section core you have for 110V 55 turns and with the formula I have 344 turn .

Please tell me I'm wrong : It will be less work to wind a transformer !

Luc Benard

P.S. I extracted this formula from a link post last week on the tesla list.
The link is call:
"Roll Your Own Power-Transformers! " I don't remember the URL I just copy
the documentation...

Tesla list wrote:

> Original poster: "Ed Phillips by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <evp-at-pacbell-dot-net>
>
> Tesla list wrote:
> >
> > Original poster: "S.Gaeta by way of Terry Fritz <twftesla-at-uswest-dot-net>"
> <sgtporky-at-prodigy-dot-net>
> >
> > Hi All,
> >
> > I have a 10KV, 23mA OBIT that burned out in furnace duty last Winter. I
> > finally got around to depotting it and found that the only part of the
> > secondary that was any good is the bobbin. I am in the process of rewinding
> > it with 34 AWG wire (much thicker than what was on there before!). I am
> > designing it to give me about 5KV total. I chose the 34 AWG because it
looks
> > like the same diameter wire that they used on a 12/60 that I also depotted.
> > My goal is to get 60mA out of this thing.
> > My question is: How much current can I get out of this thing before the
core
> > saturates and gives me grief.
>
>         Current doesn't saturate cores, voltage does!  You'll need the same
> number of turns on the primary that you had before.  If you destroyed
> the primary, a conservative rule of thumb is that the number of turns is
> the voltage divided by the cross sectional area of the core in square
> inches.
>
> <A lot of folks have written about knocking
> > shunts out of NSTs, but has any one else ever tinkered with OBIT cores?
> >
> > Thanks,
> > Sue
>
> Ed