>I am moving into that portion of Cozy building which requires the hotwire
>cutting of foam. It's been 20+ years since I've had to worry about a
>suitable power supply for a hotwire saw (note: remember to whom you loan
>tools to). The great extent of my knowledge in regards to such a power
>supply is that, Amps kill and Volts heat:)
>
>So not wanting to hook a light dimmer switch up to the house power supply, I
>decided to start looking for a Variable Transformer(Variac), I have located
>a company (All Electronics Corp) that is selling 2-types of these Variable
>Transformers, URL
>(http://www.allelectronics.com/cgi-local/SoftCart.exe/online-store/scstore/c
>-Variacs.html?L+scstore+jdcw2965fff8d9f8+963471892). Would you take a look
>at the 2-Variacs listed, and tell me if these are suitable of producing in
>Safety the heat needed for hotwire cutting the Cozy wing and canard parts.
>The Variac that interests me the most is their 5 Amp Variable (Input: 110
>Vac. Output: 0 - 130 Vac) Transformer (#SC-5M). I am also open to
>suggestions and other possibilities, but with my children assisting me in
>plane building I am not comfortable with the practice of plugging an
>non-insulated dimmer switch into an outlet and the other end attached to a
>hot wire.
>
>Could someone please shad some light on this problem:
Variacs (an acronym trade name derived from "VARIable AC") are very
handy devices for generating a source of adjustable AC voltage in
the shop. They can adjust the speed of motor driven power tools,
vary the output from small heaters, -AND- many builders have reported
success with using VARIACs to control the power to a hot-wire foam
cutter.
By-in-large, used with understanding and some caution, these critters
can be most useful. However, be aware that these are not isolation
transformers . . . they have but one winding and operate as sort of
an AC potentiometer. Just because the "OUTPUT" is a few, seemingly
non-hazardous volts, there are ways they can be mis-wired such that
terminal output voltages with respect to earth ground is equal to
your 115 vac line voltage. Take a peek at a wiring diagrams I've
just uploaded to:
http://www.aeroelectric.com/articles/variac.pdf
Most VARIACs come already enclosed and internally wired
at the factory. However, there are lots of surplus components for
sale out there that require the user to mount them in an enclosure
and/or wire them up . . . It's not difficult to wire these guys
up so that they do not present a hazard for driving your hot-wire
cutters or other exposed conductor applications. Further, its
always a good idea to operate your shop's wall outlets from a
ground fault interrupter . . . they are really inexpensive. One
GFI can be wired to supply all of the miscelaneous outlets in your
shop.
Bob . . .
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( Knowing about a thing is different than )
( understanding it. One can know a lot )
( and still understand nothing. )
( C.F. Kettering )
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http://www.aeroelectric.com
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