Re: Transformer core

Thank you all for your tips and suggestions.

I have taken everything apart and removed the original windings.  
There were about 120 turns of 12 gauge wire.  I measured an 
inductance of 220mH.  At the rated maximum load of 8A, this is 
1000 amp-turns.  I will be running at 25A, so this leaves me with a 
maximum of 40 turns.  I estimate that I will need much fewer than 
40 turns to produce 13mH.  I will rewind the core as soon as I get 
some 10 gauge scrap wire.

Matt Behrend

>  Hi all,
>  I have a large transformer core that I want to wind for my inductive 
>  ballast - 13mH.  It must handle 3kVA without saturating, so could 
>  some of the transformer experts tell me if my core is large enough, 
>  and minimum number of turns required?
>  Overall dimensions are 7.5" x 6.25" x 2.5"
>  cross sectional area 1.25" x 2.5" on perimeter sides and 2.5" x 
>  2.5" in center leg of the El  shape.
>  This is from a 1kVA Topaz isolation transformer, but the size of the 
>  core seems like it can take much more power.
>   >>
> I'm not an expert on HV or HF stuff, but seems to me all that counts is
> the 
> number of ampere-turns.  This will determine the flux density which causes
> saturation.  Generally, LF uses a larger cores than HF - the slower cycle
> times allows higher flux buildup and saturation.  It would be nice to know
> how many turns were on the original core.