Re: [TCML] RANDTRONICS Transformer

[David Dean <deano@xxxxxxxxxxxxxxxx>]

Hi

I have a transformer with core size approx. 5.5" x 6.25" x 2.5" that has output 
of 36V at 30A or 1080VA. It was from a golf cart battery charger, so has 
shunts. Yours should be good for 1.5 to 2 kVA as a transformer with a core that 
size.

As a choke, using #8 THHN, you could only get about 100 turns into that winding 
window.  Just a guess on my part, but I would expect the core to start 
saturating around 100 to 120 Volts across the coil with no gap between the E 
and I parts.   With a gap, depending on how wide it is, the saturation point 
will of course be higher, and not likely to be a problem, though the wider the 
gap the lower the inductance and the more current will flow. #8 THHN is rated 
for 55A in conduit, But in a close wound configuration it would need to be 
derated to account for the temperature rise. Ultimately the limiting factor for 
the current is heat buildup in the wire. 

Is this the same transformer as in this thread?
http://www.pupman.com/listarchives/2001/August/msg00224.html

later
deano

On Saturday 01 November 2008 06:24:20 pm G Hunter wrote:
> I'm in possession of an unknown transformer, and I'm trying to figure out
> what to do with it.  It is marked "RANDTRONICS 143A00379".  It has eight
> taps--four identical taps on each side.  I can't see the windings, as they
> are covered in stiff, black paper.
>
> The tranny weighs 47 Lbs.  It is an E I core of laminated iron, held
> together with four bolts thru the corners.  The center leg measures 2.625"
> x 3.56" for 9.35" of cross-sectional area.  The whole core is 7.5"W,
> 6.25"H, and 3.56"D.  The winding windows are 1.25"W x 3.75"H.
>
> I have two ideas for it.  Idea #1 is to rewind the thing for high voltage. 
> I have several pounds of #28 magnet wire for the secondary.  How much power
> can such a core process?  I'm guessing at least 2kW continuously, and
> perhaps twice that intermittently.
>
> Idea #2 is to rewind it as a variable ballast for my 11kV pole transformer.
>  I could wind it with #8 THHN wire, and use an adjustable gap between the E
> and I pieces for current control.  I wonder how many amps such a core can
> cope with before saturation?
>
> If anyone has a better guess as to the power handling capacity of such a
> core, please share.  Also, if you know what kind of tranny this is, please
> let me know.  I'd hate to cut the windings off something useful.
>
> Cheers,
>
> Greg
>
>
>
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