Variac Reality

Often imitated, never equaled!

While i have seen one like that, it was only that special one. All the rest are variable autotransformers (single winding) and no particular safety problems when used correctly. And they are still made the autotransformer way. Just search for current products.

John,

It's certainly true that the vast majority of variacs are a single winding, but they do make some that are truly isolated -- I own one. It's only a bit bigger than a regular variac of comparable power, so I believe it is just two windings on the single core (rather than a separate isolation transformer in series with it).

Hmm... maybe I should take it apart and post pictures?

So why not put it on the bench, and report your result, like John did?

Good Luck! Rich

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autotransformer:

Have you ever even seen a real Variac? I'd be really interested in seeing a pic of this thing you're talking about.

Thanks, Rich

Note that I was careful to say I'd never seen one, not that they don't exist.

I'm guessing that it takes less iron to separate the functions. A Variac probably has very low volts/turn, to make the sliding contact/shorted turn thing work out, so may not be magnetically efficient.

John