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RE: Self-built power transformer
Howdy, Mark !
Homegrown power transformers are not as trivial as you may think.
For instance, there is a lot of 'magic' in the design of the core.
Laminations of silicon steel are used to prevent eddy current losses which
may eat up your power if you try to substitute steel pipe. You need to
account for the reluctance of the magnetic circuit, and for saturation
effects. There are engineers who spend their careers doing just this.
Calculating the windings is just the tip of a BIG iceberg.
A popular shortcut in ham radio is to find a transformer with the power
handling capability you need, and rewind the secondary for what you want.
The primary is usually the closest winding to the core. Starting with
something like a 7.5 kVA welding transformer takes the guesswork out of the
primary and core design. Just use the original primary and core, count the
turns as you unwind the secondary, and rewind with your calculated winding.
Ham radio handbooks have some good roll-up-your-sleeves info on this.
I have heard of homegrown cores from florist's soft iron wire, and I once
made a coilgun with florist's wire, but have never built my own power
transformer core. In any case, good luck, and let us know what happens !
Will
ps volts and amps go as the turns ratio, impedance is as the square of the
ratio, power is the same. conservation of energy.
> ----------
> From: Tesla List[SMTP:tesla-at-pupman-dot-com]
> Sent: Tuesday, September 29, 1998 21:04
> To: tesla-at-pupman-dot-com
> Subject: Re: Self-built power transformer
>
> Original Poster: Mark E Finnis <mefinnis-at-medicine.adelaide.edu.au>
>
> At 16:03 29/09/98 -0600, Reinhard wrote:
>
> >Here are some values I will build my xformer with:
> >
> >Input: 240V-at-50Hz
> >Output: 15000V-at-500mA (7.5KVA)
> >Primary: 124 turns of AWG 13 (middle leg)
> >Secondary: 7792 turns of AWG 24
> >(This is total, I would ct it, so I would need 3896 turns per outer leg)
> >Crosssectional area of the biggest leg: 2.87 inch^2
>
> Confused through my lack of theory ........ AGAIN :-(
>
> I seem to recall in the previous 'home-made transformer' thread, that
> voltage step-up/down was related to the ratio of (turns^2). The above
> appears to be calculated on ratio turns.
>
> Help from the 'learned ones' requested ;-)
>
> Cheers,
>
>
>
> _________________________________________________
> Mark Finnis
> Staff Specialist, Intensive Care Unit
> Royal Adelaide Hospital
> http://www.health.adelaide.edu.au/icu
> Ph: +61 8 82224000 Mbl: 041 2324268
> _________________________________________________
>
>