On Monday, November 9, 2015 at 4:41:37 PM UTC, Tough Guy no. 1265 wrote:
On Mon, 09 Nov 2015 15:26:07 -0000, charles wrote:

In article ,
Tough Guy no. 1265 wrote:
On Mon, 09 Nov 2015 13:48:44 -0000, Dave Plowman (News) wrote:

In article ,
Tough Guy no. 1265 wrote:
Anyway, every time I've seen one of those yellow builders transformers
for sale, it's referred to as isolating.

Of course it's isolating. That refers to the design of transformer.

Hmmmm, isolating from the mains perhaps. I assumed isolating was completely isolated, as in floating.

Using an auto transformer

Oh is that what they're called, I call those Variacs. Very useful.

Vsriacs have a variable ouput. Autotransfomers can be fixed.

Seems pointless. Are they cheaper than two separate coils or something?

Cheaper, smaller, less excitation current (so less leccy wasted when current isn't being drawn from the secondary), better voltage regulation. Yes much less copper is used and a smaller core is needed.

Main disadvantage is that under fault conditions primary voltage can appear on the primary as they are not isolated.

They are used a lot on the high voltage side of the mains distribution networks.






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