[Test-Equipment] Powerstat/Variac ID

[Philip Barnes-Roberts WA6DZS]

test-equipment-request at mailman.qth.net opined  on 02/23/2009 09:00 AM:
> From:
> Phil Staton <phil at barely.me.uk>
> Date:
> Sun, 22 Feb 2009 19:26:51 +0000
>
>
> I'm not convinced I've sent this correctly.
>
> Mine of same size is rated 2KVA
> weight  (of mine) is more but I have metal sockets and cable attached 
> and I'm too lazy to take it apart
> The difference will be mine is wound for 240volt use, yours seems to 
> have thicker windings (no surprise there then)
> Phil G4FXY
> (also known as nakedphil - long story)
If you leaf through that 55-page PDF catalog from Powerstat (thanks, 
guys), you'll notice that most of the single-phase units (the easiest to 
understand, the others are duplicated etc.) have two taps at the 
'high'-side or 'Line' end.  If you need to boost a low line voltage 
(here in Altadena, for years, we saw about 104VAC at 60Hz in the summer 
in our 1910 house, and fluorescents in the garage were - hesitant - to 
start) you can put the line to the second tap and the bottom, and dial 
out to maybe 130% of the line.

Besides personnel safety, keep in mind that because the current rating 
(due to wire size) applies over the whole range, if you try to pull 
heavy current off the variable tap, at low voltage, you can fry that low 
end of the (single) winding of the autotransformer, making it into a lab 
curiosity, also known as a 'brick'...  Do you need to ask how I found 
this out, years ago? X-}

-- 
'---O=o=O---'
73, Phil Barnes-Roberts WA6DZS < Mailto:pbarnrob at acm dot org >
"BETTER is the Mortal Enemy of Good Enough" --Dave Norris, JPL Eng.