"John Larkin" wrote in
message ...
On Sun, 6 Jun 2004 16:30:39 -0400, "BFoelsch"
wrote:

It's interesting, when I learned this stuff ( I won't tell you when, but
my
then-new text was published in 1935!), albeit in the context of
utility/power engineering, about the LAST thing we learned was the tricks
and conventions about turns ratios, etc.

Just looking at a question in my book:

"Assuming a coil of thus & so dimensions surrounding a core of this &
that dimension & type of material, calculate: 1) The flux in the core, 2)
the flux in the air," etc.

Follow-up question:

"Assuming a second identical coil placed elsewhere on the core,
calculate
induced voltage if only the flux in the iron passes through the second
coil," etc.

I had to take a year of Electrical Machinery in college, including
labs with big transformers and motors and stuff. I learned a lot from
it.

The whole text was written like that. The concept of a "perfect
transformer" was introduced much later, and only in certain contexts. For
utility purposes, perfect transformers are undesirable!

Is that because they conduct short circuits too well?

Primarily. In olden times transformers were designed for the best possible
"regulation." After power systems got stiff enough, however, the concept was
changed to allow transformers to limit fault current, and the old measure of
"regulation" was replaced with the modern day "impedance."

Extra credit: What is the definition of impedance, in the transformer sense?

Answer: The percentage of rated primary voltage which will produce rated
current through a short-circuited secondary.

John