[R-390] Isolation Transformer update

[Heinz und Hannelore Breuer]

Hi Barry,

the current was probably not in phase with the voltage when running the
transformer idle, so the actual dissipated power was less than 30W to
50W. 
OTH I just checked my data books and found 93% efficiency for a 1kVA
transformer, this is 70W total loss dissipated in heat for this kind of
transformer. Iron loss alone is about 40W the rest is cooper loss both
in primary and secundary windings. 
The higher current at the 110 primary is expected because you have less
windings per volt and the core gets a higher induction closer to
saturation. Standard cores run at about 12,000 gauss, hypersil
transformers at 15,000 gauss or even higher. If you go higher the cores
hums louder. A welding transformer is a typical application were the
transformer is rated very close to saturation. But it usually only runs
a few seconds at a time.

73
Heinz DH2FA, KM5VT


"Scott, Barry (Clyde B)" wrote:
> 
> Hello, Heinz,
> 
> It is 9A with the windings connected in parallel (1kVA) (4.5A per winding).
> It is a very nice unit and I think it is okay, I was just a bit surprised
> that it drew that much current at "idle".
> 
> Thanks,
> 
> Barry(III) - N4BUQ
> 
> > Hi Barry,
> >
> > didn't you mention before that the transformer is rated 9A or was this
> > per winding and doubles if used in parallel? Anyhow you have either a
> > 1kVA or even a 2kVA transformer and for something like this
> > about 30W to
> > 50W iron loss is quite good. You will get some cooper loss too at
> > maximum current but this is well within specs.
> >
> > 73
> > Heinz DH2FA, KM5VT
> >
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