Now my ISP has switched me back on...

"Chuck Harris" wrote:

[see below]

I take capitals as shouting. That is usual, I believe. You shout
sometimes.

It has been said that saturation depends on voltage. It has been
said that in order to avoid saturation the core should be made
bigger. You began yourself by explaining that the problem would be
related to skimpy margins of iron and copper, neither of which is
relevant and seems a bit like axe-grinding to me. For the same
quality transformer at twice the voltage Casino requires the same
quantity of both.

The impression of emphasis, and I did say emphasis, is because much
has been said about size of core, and virtually nothing has been
said about number of turns.

Yes, what you said about economy of materials is true, and yes you
can argue as has John that you merely meant that the symptom of
saturation appears in the core, rather than the cause.
Nevertheless, by not mentioning number of turns, which is the crux
of the matter, the impression was created. I was not the only one
who had difficulty following a thread that drifted towards the
moans of small producers in the face of the bean-counting
Juggernauts, blah.

The maths bits are fair enough but rather generalised with respect
to the original question of what would be the problem with that
particular transformer at that voltage. That left a gap, between
the reminiscences, the business interests, and the maths, where I
felt a simple answer might have been.

As far as "boning up" is concerned, I had failed previously to grasp
the point that currents due to load cancel, more or less, with
respect to saturation. Something I had not noticed in the fog of
knowledge
I already have. There is a reason for this that I have just been
wondering about. It explains why my spice transformer model still
has a linear core. I must have known everything else that is in the
model otherwise it wouldn't work, I suppose. Specified transformers
seem to work OK, so I guess I must have known something then...can't
really remember. Must have though because some of my transformers
are quite complicated and have quite a lot of wires coming out of
them.

And for audio-intended transformers you don't really need to know.
Saturation will be outside the full-power bandwidth. Er...I think
that follows anyway...yes it must.

On the face of it, as I have said somewhere in this thread, all I
need to do is regress the BH curves of GOSS and NOSS onto a
quadratic (or whatever) expression spice can understand. I
don't carry maths in my head. Never could. Always had to derive
from first principles every time until computers. Never completed a
maths exam in my life. Dunno how I passed so many, a currupt
education system I suspect. Anyway I have found that Xspice has two
complete transformer models with core, requiring a set of
co-ordinate pairs for B and H, which is encouraging, plus core
length and area. If I discover it in my own system I'll show you a
picture.

I am fundamentally uneasy about saturation. Coming from a
background with no practical electronic content, I still am
conscious of mapping mechanical dynamics onto electrical things.
But I have never needed to consider the saturation velocity of mass.
Or even its equivalent of the BH curve. Never been into rockets and
stuff, or really big things, or really small things moving very
quickly. Ballistics is about my limit.

What I say is related to my purpose here, which is not to
demonstrate what I know. I have never to my
knowledge been responsible for electrocution, and am careful to
frequently point out that I know virtually nothing about anything.

Your original comment to William:

Please don't give advice about things you don't understand.

Is pathetic and silly. This is a discussion group. I give opinions
on lots of things, and got sick of putting "IMO" in every sentence.
If there were only Chucks here, and no Williams, there would be no
point in coming. But William employs a similar strategy to me, it
seems, and it was his perseverance, despite your bullying, that
sorted the wheat from your chaff.

The rest of your first contribution was pure hyperbole, intended no
doubt to rub in your bullying with a bit of guilt-tripping.

If you try applying 120V, 60Hz to this 60V, 60Hz winding, you
will drive the transformer well into saturation. This will
cause
the primary current to approach that of the DC wire resistance.

In a word, You will let all the smoke out of your
transformer.

Only if he gets an arc. No poof. Much slower than that. Care to
bet? A current can't approach a resistance, BTW. Pedantry, yes,
but OTOH that sentence doesn't make sense anyway. Approach usually
implies that it gets close. We don't actually know how close it
would get, because we don't know for what proportion of the time the
core would saturate. There will be a lot of margin to play with, in
terms of power rating of the windings, so I would expect minutes,
not seconds, before destruction. You'd notice, wouldn't you? The
buzzing, the noise, etc. You wouldn't just walk away and let it
burn.

cheers, Ian

Hi Ian,

I have no axe to grind, and I don't shout and squirm. If you
feel that I do, perhaps it is your own prejudices at play. When
I make mistakes, I admit to them, and try to correct them... if
possible.

I have read the whole thread on "Reversing a Power Transformer",
from beginning to end, and I must have missed the point where it
was stated (or implied) that core size is dependent on voltage.
If I, or others, have stated that, it was an error, and needs to
be corrected.

In so far as I can recall, I have never believed that voltage
determines core size. This isn't a recent revelation, I designed
and constructed my first power transformer around 1974. It was a
whopper that delivered 20V at 30A. And stayed very cool and quiet
at anywhere up to full loading. I used it for 15 or so years
in a power supply of my own design. I have since sold the power
supply, and as far as I know, it still is working. In the years
that have passed since the design of that transformer, I have
designed and built a forgotten number of linear and switching
power transformers and inductors. The latest of which, was a
100KHz switcher that was part of a battery charger system I
developed for the US Army.

You are rapidly growing more correct in your statements about
transformer design and characteristics. Your postings, up until
this last couple, had what I interpreted as strongly misleading
statements. I suspect that you have been boning up on the art
of transformer design, and that is good.

-Chuck

Ian Iveson wrote:
"Chuck Harris" wrote in message
...

Ian,

Please point out the article that "concentrates only on primary

voltage

and core size".


Only if you promise not to shout and squirm. Is there anything
else
you think I have got wrong, or is the rest of what I have
written
here correct? You appear to wish to grind an axe rather than
clarify the truth.

Ian