In article , "Ian
Iveson" wrote:

"John Byrns" wrote in

For mains trannies they require the voltage to be specified, but
it
has no effect on core size.

The input voltage and frequency for a mains transformer are fixed
quantities, so it is only natural to rate the windings in terms of
these.

No, John. The original question demonstrates that
input voltage is not a fixed quantity. That is what the pertinent
parts of the thread are about.

Yes, Ian, the input voltage is a fixed quantity, here in the US the
domestic supply voltage provided to residences is 120 volts at 60 Hz, in
Europe it is something different, but still fixed. The original posters
question was, can I hook the 60 volt winding of a power transformer to
that 120 volt supply without damaging the transformer? It is not
necessary to get the data on the core and calculate current to provide a
reasonably accurate to that question. My point is that I am not a
transformer designer, I am only a user. Sure the transformer designer is
going to do all the current calculations you talk about, but why should I
do that as a user, when I can much more easily determine approximately
what voltage a transformer winding can handle at a given frequency, based
on the original voltage and frequency ratings of the transformer, which in
commercial grade power transformers bear a close relationship to the
saturation point?

The core size has nothing to do with voltage for a given quality
transformer. I'm sure you know this really. You're just trying to
wind me up.

Although I may be mistaken, I don't think I have made any claims in this
thread about core size vs. voltage, I don't think I have even mentioned
core size. I think you are confusing my comments with those of someone
else. You are the one that insists on injecting core size into the
discussion.

I'm not trying to wind you up, I'm simply saying that from the perspective
of a user of power transformers, the voltage spec. of a winding is the
most relevant for determining if a given voltage will saturate the core,
the current is only of interest to the transformer user in calculating the
power the transformer can pass without overheating. As a user,
calculating the saturation point based on current is a much more complex
undertaking than simply looking at the rated voltage and frequency.
Calculating saturation based on current requires me to have knowledge of
several characteristics of the core, and do relatively involved math, why
go to all that trouble when I know approximately how commercial power
transformers are designed with respect to saturation vs. voltage, and
frequency?


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/