Godfrey Loudner wrote:
It's too bad we can't get hold of the sophisticated software
companies use to design transformers. The ones I saw advertised on
the web cost about $80,000 or can be rented. They seem to use finite
elements to deal with the horror of the differential equation
involved. The programs can even deal with the thermodynamics of the
transformers. I'm beginning to believe that the details of the
mathematical methods are kept secret for financial reasons. The
software Mathematica keeps some of their methods secret and that is
a real horror. It would be much fun to enter the geometry of a mot
or NST and run the calculations in particular cases. Godfrey Loudner
There's no secret math in finite element programs like Maxwell or HFSS
What you get for your tens of $K is a useful user interface, both for
data entry and for looking at the results, lots of library support in
terms of materials and prebuilt models, etc. You also get good
interfaces to CAD/CAM software (so you can model the part you're
actually going to build, without having to re-enter the model)
They also have fairly efficient computational algorithms for doing the
FEM, rather than brute forcing it with a tiny time step and hoping
that numerical precision doesn't bite you.
All of this costs real money to write in the first place, and it saves
engineers time to use it, so they can justify the price they charge
for it. If a senior engineer costs about $250k/yr (salary, benefits,
office space, etc.) and you save 20% of their time, you've just
justified an analysis program that costs $50k/yr. Whether or not an
engineer spends enough time doing analysis (as opposed to adjusting
Gantt charts in MS Project and doing powerpoint presentations) is
another factor, but I will say that modern design/analysis tools are
wonderful.
There ARE open source/free analysis codes out there, but after using
them, you'll see why folks are willing to pay the kilobucks, if
they're doing it for work. The free codes are often limited in terms
of model size, or require you to write software to describe what it
is you are modeling (i.e. you get the FEM grid stuff, but YOU have to
load the grid and constraints), or were done as a senior
project/master's thesis, and are 90% complete and untested, or, are
some toy built in BASIC back in the 1980s as demo on a TRS-80, etc.
They won't import IGES or DXF, etc. They might have bugs. They might
require doing many runs to understand numerical precision effects (you
can't just chop things up into a really fine grid and sum them all).
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