Will Matney wrote:
> Steve,
>
> First, everyone in the industry uses gauss. 1 Tesla is 10,000 gauss which he
> uses Tesla. You can use Tesla to shorten the number. However, when you read
> any book on the subject, the formulas use gauss. The magnetizing force H or
> Oersted has a lot to do with it too. As flux density rises, so does the
> magnetizing force. He also uses square meters, and where is a core a square
> meter unless in a huge transformer. Most all published formulas use square
> inches or centimeters. He also goes the hard way on the main formula using
> division after division ( t = V(RMS) / 4.44 / m^2 / Hz / T). It's much easier
> to multiply everything, and do one division. By the way, the 10^8 I show in
> the long formulas must be multiplied by the voltage so that it can be divided
> after multiplying everything.
I can't speak for iron cores, but all the data I've been studying
recently for ferrites uses SI units - Teslas and m^2 or mm^2 - there
again, it's data from European or Japanese manufacturers. I guess cgs
units and inches might be more common in the US.
>
> Also, the author never mentioned the watts per pound losses of the steel
> which rises with increased flux density. The short formulas I showed for core
> size from output power and the turns was developed from the experience of
> engineers years ago, and has been used ever since. They can be recalculated
> for different frequencies. All of this goes into the efficiency of the
> transformer, and has to do with its regulation too. I think he's
> over-simplifying the design process, leaving a little out, and making the
> math harder to do. There's just a little more to designing one in the real
> world than that.
There's usually a bit more than anyone can put into a simple document -
but as someone who fits (or at least fitted) the description in his
opening lines, I found it very helpful. It's probably because the way he
puts things happens to 'click' with me.
73, Steve
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