How does your iteration compare (in size and weight) to a commercial
product rated for a 50degC rise, with the same ratings?
While commercial products do tend to be rather cost conscious,
nowadays this means M16 or better grade lamination and use of
intermediate wire guages where necessary, to provide a smaller part
with a ~ lighter shipping weight.
While size and temperature rise may not play an important role in
one-off prototyping, we are all using roughly the same tools and
materials in 50/60Hz isolation devices.
This results in a situation where the 'winner' may have the insulation
system with the higher permissible operating temperature, smallest
package or lowest assembly/shipping cost. Every application has it's
own priorities, and every sale has it's clinching salient hook - one
that may have nothing to do with 60Hz magnetics performance at all.
This shouldn't prevent a designer from tackling the goal of optimizing
designs within the operating environmental constraints of the power
level addressed. In order to do this, it is important to refer to
specific material grades, lamination sizes / stack heights and
temperatures predicted/recorded (in degrees of a recognizable scale),
when describing an iteration.
I'm not sure what formulas you were refering to earlier, unless you
meant the original poster's web reference, ie:
( members.tripod.com/~schematics/xform/xformer20.htm ) If this is the
case, then core size is being selected by means of a curve-fitting
guideline that does not reference either target magnetic material
grade or design temperature rise. While these obviously entered into
the equation originally at somepoint in time, being related to power
loss at the throughput levels charted and flux density proposed in a
square lamination, they should be stated.
Unlisted insulation systems are usually restricted to applications
where rises are demonstrated not to exceed 30degrees C above the
ambient temperature. Listed insulation systems for higher operating
temperatures are offered for use, free of charge or reassignment, by
many varnish and insulation material manufacturers.
http://www.pdgeorge.com/
http://www.dolphs.com/
http://www.pleo.com/index.html
http://www.e-insulationsys.com/english/select.lasso
RL