There is usually "plenty of room" in the calculation tolerances and 
for most designs 50 Hz or 60 Hz does not make any difference. Same 
for 110 Volts or 120 Volts. Most transformers are calculated for 
mains +/- 15 %, there again, plenty of room. You have to try very 
hard to drive the cores to saturation. Are you sure of the way you 
have connected the windings connected to the mains. Try with one 
winding only, you will have half the power available but you can 
check for overheating, try with the other and if it runs cool try 
connecting both.
then you might be able to see where the problem is coming from :-)

At 00:04 30/11/2006, you wrote:
>Daniel Dourneau wrote:
> > 50 Hz or 60 Hz operation should not really make any difference.
> >
> > What I cannot understand is why your transformer gets so hot in the
> > first place. Is it under rated? What is your load current? What type
> > of rectifier are you using (bridge, single diode)? What value is the
> > capacitor.
> >
> > One thing is sure, if you cannot touch it, its too hot and forget
> > about any type of certification of your product (if you intend to
> > apply for that)
>
>Each winding of a transformer is an inductor, so 50Hz/60Hz does make 
>a difference
>to the current that flows. Current will be higher at 50Hz because 
>inductive reactance
>is lower (Ohms).
>
>I tested it no load (open secondary). No diodes,caps or anything.
>
>I agree: it's too hot. Perhaps the combination of 50Hz and 120V 
>(slightly above the
>nominal 115V) pushes it to the edge of magnetic saturation and hence 
>a dramatic
>increase in temperature. In that case I'm dissapointed. But I will 
>test a bit further yet.
>
>--
>Brent Brown, Electronic Design Solutions
>16 English Street, St Andrews,
>Hamilton 3200, New Zealand
>Ph: +64 7 849 0069
>Fax: +64 7 849 0071
>Cell: 027 433 4069
>eMail:  brent.brown@clear.net.nz
>
>
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