On Wed, 22 Nov 2017 14:39:04 -0500, "J.B. Wood"
wrote:


Hello, and do you have a particular make and model number of device in
mind? An marketed as an AC isolation transformers usually doesn't
provide voltage conversion with input (primary) to output (secondary)
energy transfer solely via magnetic coupling. There are also adjustable
autotransformers (e.g. the venerable Variac brand) that, for example,
takes 120 VAC at input and can provides 0-130 VAC output. The primary
and secondaries of these devices aren't conductively isolated (as an
ohmmeter test will confirm). There are also devices which combine both
isolation and adjustable autotransformer function in one enclosure. Or
you can simply take, say, a 120 VAC-to-120 VAC isolation transformer and
follow it with an adjustable autotransformer, keeping in mind the
maximum AC current/power ratings of the devices. Sincerely,

I reaad on some website where someone took two 120 to 240 volt
transformers, connected both 240 windings together and ended up with 120
on the secondary, completely isolated from the AC line. This makes
sense, for someone who has two such transformers on hand. But would not
make sense to buy two transformers.