Re: Rewinding BIG transformer

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

Original poster: "Mike Novak by way of Terry Fritz <twftesla-at-uswest-dot-net>" <acmnovak-at-msn-dot-com>

Hey Jason,
Check out the xformer winding page at http://allencoilpage.home.att-dot-net/
There's all the good equations you'll need.
This is the best transformer winding guide I've come across thus far.


-Mike Novak



----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, March 25, 2001 12:21 PM
Subject: Rewinding BIG transformer


> Original poster: "Jason Johnson by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <hvjjohnson13-at-hotmail-dot-com>
>
> Hello,
>
> Yesterday I got back from a state surplus auction that had equipment from
> around lower Michigan. I managed to score a huge transformer for cheap (50
> bucks!) there too. The transformer as it sits is good for stepping 2400
delta
> down to 480 delta at 112.5 KVA (no thats not a typo). This thing is huge!
It
> weighs in at 950 lbs (we had fun getting it off the truck, my back is
still
> sore!) and is the size of a small refrigerator! It has a core area of
about 25
> inches^2 and is the standard EI core type, only the core is about 2 feet
long
> and 2 feet tall.
>
> What I was wondering was if I could rewind this beast for about 30kv at 24
KVA.
> The only thing is I want to do this as cheaply as possible (read: as few
turns
> as possible). Solving the equation:
>
>  A=74*PV/(f*PT)
> where:
> A= cross sectional area of the core in square inches
> 74= guesstimated permeability of the core material (has worked well for
all the
> transformers I have)
> PV= Primary voltage
> f= frequency
> PT= Primary turns
>
> for PT:
>
> PT=74*PV/(A*f)
> And putting 240 in for PV, 25 for A, and 60 in for f; I get 11.84 for PT.
> Is this right? Only 12 turns for 24KVA? Are my calculations screwed up? By
this
> same number I would only need 1500 turns for the secondary! I like these
> numbers, but I'm afraid that they're not right!
>
> Comments?
> Jason Johnson
>
>
>