On Sun, 13 Jul 2003 00:24:40 +0100 "Ian Iveson"
wrote:

This is quite an interesting article, Jim.

http://www.metglas.com/downloads/lit..._dist_appl.pdf

It has commercial interests attached of course, and compares GOSS
with amorphous iron, but is informative nonetheless.

Okay, I looked it up and read it. It's mostly a historical summary of
METGLAS with a bit of technical data in there. It seems mainly to be
aimed at selling METGLAS core power transformers to the power
industry. Some of the data looks interesting, but most of it is given
without explanation, such as the data on telephone interference....

One thing that seemed really odd was the section claiming to show that
a METGLAS core would have a lifetime of at least 30 years. They really
didn't come right out and say that METGLAS cores deteriorate over
time, but the implication is there, and this would certainly bother me
if I was considering investing in a bunch of them. Transformer cores
should be durable over centuries or longer. If this stuff breaks down
in decades it's got an uphill battle ahead of it.

There's also nothing in there about the comparative economics of
making high efficiency transformers by simply using a bit more iron
and copper. This has become popular in transformers and motors in the
past couple of decades and may be a better investment than a METGLAS
cored transformer.

Nothing that I could see on transformer design proceedures other than
specs on saturation flux density and the very narrow hysterisis curve,
which shows low losses.

Certainly nothing about running a given transformer at twice the
design voltage.

SO who's got that transformer? Can we actually do the test and settle
the debate?

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------

On Sun, 13 Jul 2003 02:29:47 -0500 "Tim Williams"
wrote:

"Jim Adney" wrote in message
.. .
Sure, that's a no brainer. If you have a commercially built
transformer with a winding rated at 120V/60 Hz I would be ready and
willing to bet that it will be in instant trouble if you put 240V/60Hz
across it.

Let's try it!

Uh oh...

*Wraps arms tightly around stock of transformers*

Don't worry. For peace of mind I'd include a fuse anyway. Fuses are a
lot cheaper than transformers. ;-)

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------

"Jim Adney" wrote in message
...


Bring some stuff to sell or just to show off!

Maybe we should just bring a stock of antique transformers and blow
them up by running them on 240V. You know, sort of like the engine
blows they do at drag races... ;-p


Little late for the 4th of July, isn't it?

jim menning

Jim Adney wrote:
On Sun, 13 Jul 2003 15:49:18 GMT "Jim Menning"
wrote:


"Tim Williams" wrote in message
...


Jim Adney
Madison, WI 53711 USA

Hey whaddya know, I'm in Beloit!


Then I expect both of you to be at the Wisconsin Antique Radio Club
swap meet in Milwaukee next weekend.

Bring some stuff to sell or just to show off!


Maybe we should just bring a stock of antique transformers and blow
them up by running them on 240V. You know, sort of like the engine
blows they do at drag races... ;-p

Considering that so many Airline and Zenith (yeah, blame it all on 6X5s)
are barely capable of 125 volts, this could be a sleeper. They'll burn
up before the crowd gets seated.
-Bill

"Jim Adney" wrote in message
...
Don't worry. For peace of mind I'd include a fuse anyway. Fuses are a
lot cheaper than transformers. ;-)

Not to mention the $0.05 fuses being protected by $15 three-legged fuses

Tim

--
In the immortal words of Ned Flanders: "No foot longs!"
Website @ http://webpages.charter.net/dawill/tmoranwms

Jim Adney wrote:

On Sun, 06 Jul 2003 08:34:29 -0400 Chuck Harris
wrote:

Ian,

Please point out the article that "concentrates only on primary voltage
and core size".

That would be my posts. I've tried to lay out the theory, but I
realize I'm swimming against the current here, even though I'm
probably one of the few here who's actually made a living doing this.

There are others here who also clearly understand, and I appreciate
their posts, but we are in the minority.

Most people here are just going on what they have gleaned from a few
web sites and don't really understand the theory. Once you understand
the theory you will quickly understand why any transformer designer
will want to know voltage and frequency first, and power (or current)
right after that.
Jim Adney

Jim, some of the comment others have made remind me of a ham I went to
high school with. He was building a linear with a 304TH and he needed
to wind a plate transformer. He found a surplus core and unwound it,
then called me to see if I could tell him where to #2 AWG magnet wire to
re-wind the primary of his plate transformer.

He told me he had calculated that he was going to wind a 10 turn
primary, put a single layer of wax paper and wind a secondary, and only
fill about one third of the core with copper. It took a lot of
explaining that it wouldn't work, and why. He just couldn't wrap his
mind around the relationship between (turns per volt, core size, and
frequency), even with the math in front of him.

He believed the only important numbers were the turns ratio, and he
planned to use 500 Circular mils per amp. He was convinced his 24 volt
per turn would work as well as the proper numbers, and the only reason
he finally wound it with the proper wire was he couldn't find the absurd
size he wanted.
--


Michael A. Terrell
Central Florida

I realize that most people here are not comfortable with a lot of
equations, but you won't find a LOT of equations here, or a lot of
difficult math. The truly amazing thing about this stuff is that it
really is so EASY once someone lays it all out for you.

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------

I have been lurking, just reading the posts about reversing power
transformers. A step down xformer from 120 to 60 volts has a totally
different kind of winding for the primary and the secondary. Before you
shout "DUH", think about the turns versus the voltage in the primary. That
choice of wire size and number of turns in the primary is not accidental. It
is based on current capacity, flux saturation in the core, inductive
reactance, many factors. I promise you, with today's price point
engineering, there is not one extra turn on that primary that is not
absolutely needed. Having said that, you just flat don't have enought turns
on the secondary to use it as a primary. Additionally, if you have torn
apart enough power transformers, you know well that the primary is almost
always wound next to the core. That is not accidental either. The reason
that winding is on first is to ensure adequate coupling of the winding turns
to the core structure. These are simply observations on my part, but they
sure make sense to me.
Regards,
Tom