I also have used the regulating transformers at large commercial on shore
radio/computer installations. Sola was the brand we used, one on each leg of
3 phase shore power. Some critical units had small single phase
transformers mounted in the rack. They covered about 95-135 volts in for
constant output. However, they take several cycles of power change for the
change to be seen at the output. I got into trouble having a large UPS unit
feeding the transformers, as the transformer change was slower than the UPS
and we got into a voltage bucking problem. Ended up taking the transformers
out and just using the UPS. Do a web search for Sola line regulator
transformers (they are really a mag amp autotransformer device). E-bay has
them from time to time.

Doug K7ABX

"Leanne" wrote in message
...
In one radio station in which I worked, they had some regulating
transformers
that
would give 118 vac out with 95-135 volts in. There were taps to run it off
220,
which
they did, with an input of + or - 20 volts for 230 out. There was one
thing that
should
be noted is that they get very warm if running near the rated load. They
also
used to
hum a bit.

Leanne