Variac Reality

May God have mercy on your soul. You just threw a bloody steak at a rabid badger. I can hear Slaughter starting up Acrobat as I type.

Flame by pdf...

--

John Devereux

I have to say I'm flattered by the quality of the attention I got from Slaughter. No one's ever gone to the trouble to put me in a PDF of their views. It was a nice moment, I savored it.

Yeah, I was left out for some reason :(

Maybe one day. Must Try Harder.

--

John Devereux

Um, you forget the mutual inductance. You don't get it... see my paper I created just for you:

If you even would check it..

It's not the individual inductanecs that form the voltage divider but the total inductances

V1 = M/(L2 + M)*V

That is identical to the voltage divider effect or impedences when you consider the total inductance.

I measured some things and reported the results. My last comment, about independent inductors, was a snipe at your claim that M doesn't matter. In fact, winding all the wire on a single core reduces Zout by about 100:1.

You don't get it... see my paper I

Both bad links.

Do you own a Variac?

John

It doesn't matter at all to me if he owns a Variac or not...

...Jim Thompson

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| James E.Thompson, P.E.                           |    mens     |
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No, I said it doesn't matter with regard to the voltage divider rule... see the paper. You guys don't read well do ya? Or maybe you just don't understand basic math and abstraction?

2nd link works.

Yes I do, your point? Do you want me to measure the inductance of each half? As I already said, it depends on the mutual inductance... look at the paper and you can see... I bet you won't. I bet your just like the rest of the tards in here.

Surely you can follow basic math?

I'm curious why the idocity in this group? Shut me up by proving my math is wrong or that my assumptions are wrong(completely wrong).

Not for me. Complains about my browser or something. Sort of a blessing, actually. I don't need a big semi-literate PDF file to tell me that voltage is linear on wiper rotation.

I did learn a couple of non-obvious things about Variacs. I'm especially impressed that the idle current is low and doesn't change with wiper position and that the adjustment resolution is so high.

What is this thing you have about doing tons of math to show how smart you are? Lots of kids can do simple algebra. Pretty droll, in my opinion.

Designed anything cool lately?

John

"John Larkin"

** The idle current ( really I mag ) is low for the same reason all toroidal transformers have very low I mag values.

Something to do with the design of the core ......

Adjustment resolution is quite fine - long as you are prepared to play with the knob a lot ( pun intended ) - but this is a nonsense as the AC supply voltage varies moment to moment by far more.

However, voltage regulation ( at rated amp load) goes to hell at low settings - from maybe 4 or 5 % at mid setting it falls to circa 40% at a couple of volts.

As I said in an earlier thread, using a variac to supply low AC volts is plain NUTS.

..... Phil

Your response to my post (thread "How many steps in a Variac", Feb 9), was just flat wrong. The brush does interpolate to better than 1/10 of the voltage between turns. You flat denied that (even though you claim to own a Variac) and you went on to model the variac as a 2-terminal rheostat.

Waving around a bunch of pages of algebra is useless if you don't understand the physics.

Here's what I said

Which is true, by experiment. It was a simple statement to the >Thats simply not true(for the most part). It will take ignore any windings

etc.

It's not a variable resistor! It's not a 2-termial device! The brush does interpolate the turns voltage! Your math sucks!

John

ok, maybe that last part does have some emotional content.

A variac is a variable transformer. It contains a primary winding with full supply accross it. A secondary winding is placed atop this and has one end as a variable tap. It is not a single winding.

Such an un isolated single winding would be dangerous, and would not pass safety legislation.

cheers jacko

"Jacko the Jerkoff "

** Nonsense.

It is a variable auto-transformer.

** There is only one winding. ** Nonsense.

It is a variable auto-transformer.

** BOLLOCKS.

A variac is an item of * test equipment * and so need not meet normal safety regulations.

Most have terminals on the front that can deliver LETHAL voltage to any user.

YOU ANENCEPHALIC PRICK !!!!!

...... Phil

--- How so?

For a voltage divider:

E1 | [R1] | +----E2 | [R2] | 0V

where:

E1 * R2 E2 = --------- R1 + R2

E2 changes linearly with the change in ratio of R1 to R2.

In your:

M x = --------- L2 + M

x does not change linearly with changes in M.

news: snipped-for-privacy@4ax.com

JF

Tell that to the many Variac makers. Every one I've seen is a single winding.

Why do newsgroups attract so many people who make declarations that are flat wrong, about things they know nothing about but could research in a couple of minutes?

When isolation is needed, a Variac is usually combined with a separate isolation transformer.

John

Really, that's a shocking thing to say.

John

Wow, I like the use of emphasis spaces. Really drives home the point. Almost like the spaces give time for the words to echo a bit. Is it bad that I immediately thought of an anencephalic fetus in a jar when I saw that word? Damn Mutter Museum.

We all drop bullshit from time to time. The problem is that newsgroups won't let us just walk away from it. With practice we learn to choose our on-line words carefully, but some of us are slow learners.

-- Joe

Phil is an artist.

John