Variac nonsense

Feb 13, 2009 87 Replies

I have not made anything lately, but I have used a few variac cores for transformers, winding turns over the core and orginal primary. I even made a choke for a welder. Had to cut one side of the core. That was about 8 inches across the diameter. Good to clean out the grooves in the track and give a coat of enamel. You can also use it as an autotransformer with better efficiency than the variac.

greg

Since a VARIAC works like a voltage divider, I seriously doubt whether he was referring to a rheostat. JF

You'd have to ask him what he meant. It could be used either way.

I said "potentiometer."

John

So you did. Somehow or another I read "rheostat"; sorry \'bout that... JF

I can't speak for Phil, but I've got 40 year's BS in the school of Hard Knocks. ;-)

Cheers! Rich

At the point at which one is utilizing the device in a manner other than it was made for, one can also hook said device up differently. It most certainly could be used that way (rheostat), just not very well, and it would require fudged connections, which, I would add, would be required to use it as a potentiometer as well.

Fudged connections? How?

John

short lived one !

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And you sincerely believe that?

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"GregS"

** The primary winding of a toroidal, wound iron strip transformer makes a god awful inductor PLUS will saturate at a very low current level.

Same goes for a variac.

...... Phil

I'll grant you that theoretical possibility, but I'd question whether it's properly called a variac in that context, even if that's what the gear was designed to be.

Sylvia.

That he didn't calculate the power efficiency? Semi-sincerely.

John

40 years of BS, i can believe that.

Why? They are big enough to dissipate a hunk of power, and if you stay within the brush ratings, it's a perfectly good rheostat.

John

Sorry John, but even a dope like you should know the difference between the way a potentiometer gets "hooked up" and the way a rheostat gets "hooked up". Even when one uses a variac to configure in such a manner.

I am sorry that your stupidity level is such that even I cannot give you enough information to wrench you out of the stupidity barrel you have wedged yourself into.

So why fudged connections? The only thing you don't have direct access to is the top of the autotransformer winding. But you do get direct access to the bottom, so the full range of copper is available as a rheostat.

John

In the same sense that a variac remains a variac when it\'s being used as a variable DC voltage divider, a hammer remains a hammer when it\'s being used as a doorstop. JF

And her brain remains as dead as Lincoln's is at ten feet immersion beneath the concrete

Not that it maters, but if used as a speaker volume control it does much better used as an autotransformer than as a rheostat, though it works either way. Go ahead and try it if you like.

That would mean that not a soul on earth would ever respond to you then.

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