Re: POWERSTAT Variable Autotransformer... what can I do with it???

corrections: life of an incadescent bulb is the 13th power of voltage (well
the inverse thereof) so a small increase in voltage dramatically decreases
life - formula from my light bulb handbook.

sell the thing on e-bay, get $$$ if you dn't know what to do with it - they
are very handy


"DoN. Nichols" <dnichols@xxxxxxxxxxx> wrote in message
news:ebg3pt01ptf@xxxxxxxxxxxxxxxxxxxx
According to <stans4@xxxxxxxxxxx>:

Bruno wrote:
I found this item on the from steps today... my kind neighbor thought
I could use it. But I have no idea what it'll do.

The plate says...

Powerstat Variable Autotransforer

[ ... ]

AKA "Variac", which is a trademark.

Yes -- "Variac" was the trademark for those made by General
Radio. I usually think of "Powerstat" as being made by Superior
Electric, though yours appears to have Western Electric on the
nameplate.

I've used them for bringing old
tube radios back, it sometimes helps to reform the old electrolytics at
low line voltage before bringing them up all the way. We used to use
them with heating mantles in chem lab for temperature control in
distillation setups. I've also used one with a low-voltage train
transformer supplying a homemade hot-wire cutter for cutting insulating
foam pieces. Handy for a lot of things where you need variable line
voltage. You can control small AC/DC motors with it, the kind with
brushes. Incandescent lighting, too, up to the rating, anyway.

You can crank them above the rating as well -- they will get
brighter, and have a *much* shorter life. IIRC, the life of an
incandescent lamp varies inversely as the 4th power of the voltage, so
running a 115V lamp at 135V would result in a life which is about 53% of
the life at 115VAC.

Note, if it's just the bare widget, you're going to want to put it in a
well-insulated housing. There is no isolation on these, you can juice
yourself pretty good touching the right location. Hope you've got the
knob, too. G.R. wanted a fantastic amount just for a bakelite knob for
their units and you WILL want a well-insulated knob.

Well -- General Radio (GR) did have a copyrighted knob design
which looked really nice on equipment -- and a very well made one as
well, with a good brass insert to carry the threads for the setscrews
which locked the knob in place.

But one of the problems with Variac and Powerstat knobs is that
they have a larger shaft (3/8" IIRC) than the common run of electronics
equipment, which used 1/4" shafts. And the really big Variacs used 1/2"
shafts, IIRC.

With General Radio, at least, the shafts were Bakelite over a
steel core, so you had some insulation to start with -- but a good knob
makes it a lot easier to control.

I think that all of the bare units were designed so you could
mount it by ears on one end, and could adjust the shaft so the knob
could be attached at either end, depending on other requirements.
Sometimes, it had to pass through a control panel, sometimes it had to
stick out the back so the metal safety cage could be mounted to the end
with the flange.

If it's like the packaged units we used in chem lab, it'll have a nice
rounded metal housing with the knob on top, a fuse, dual grounded
outlets and a toggle switch on the side. These ran several hundred
bucks from the stockroom.

Hmm ... that is one style, and fairly common with Superior
Electric, but the more common lab-use ones from GR were in a rectangular
housing, with the knob on one face of the box, with switches and circuit
breakers on the front, outlets on the top, and (sometimes) a pair of
meters to allow you to monitor both voltage and current.

Really old GR ones -- in the days when the finish was black
instead of hammertone gray, were often cylindrical, with a base, and a
face joined by standoffs for rigidity, and a perforated *** metal
wrapped around the outside.

I've got some of both brands unmounted, and a Superior Electric
one mounted in the cylindrical case with a box on one side for the power
cord in and the outlet. It was wired rather strangely, and I had to
take it apart and re-wire it. Someone had it wired to accept power
between ground and neutral, not hot and neutral. I hate to think of how
the outlet with which it was used was wired.

Enjoy,
DoN.
--
Email: <dnichols@xxxxxxxxxxx> | Voice (all times): (703) 938-4564
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