Re: Staco variac rating differences

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Richard Williams by way of Terry Fritz <twftesla-at-qwest-dot-net>" <richardwwilliams-at-earthlink-dot-net>


----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, January 10, 2002 10:44 PM
Subject: Re: Staco variac rating differences


> Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<davep-at-quik-dot-com>
>
> Tesla list wrote:
>
> > I've recently aquired another variac. I have two Staco variacs,
> > 2510s, rated at 140v -at- 25 amps,120v input and has 5 terminals.
>
> > The third, type 033-6565, the one I just got, is rated at 20
> > Amps 0-180V, input 120V but has only 3 terminals. ???????
>
> Not uncommon.
> As noted previously, some devices provide two terminals
> at the same point for ease of wiring.  Others, specifically
> variac type, tap the coil a bit in from oneor both  ends,
> this allows them to provide outputs above the input.
>
> > huh?
>
> > Some physical characteristics:
>
> > -The wire size is the same for all 3 variacs, #12.
> > -All have the same brush, interchangable, with no apparent
> > differences in size or shape. Totally alike.
>
> > -The winding of the 033-6565 is about 3/4" taller than the
> > 2510s but has the same diameter.
>
> This makes sense, as the 03306565 has the higher current
> rating, right?  If so, it would need a 'thicker' (larger
> cross section) hence 'higher' core.  There is enough
> margin in the wire and brush ratings to allow use of common
> bits in both designs.
>
> > -The mounting hole "footprint" is also identical for the 2510
> > and 033-6565.
> > -Shaft sizes are alike at 1/2" diameter. The lengths are the
> > same.
>
> > I have several questions:
> >
> > 1) How can the 033-6565 have 120 input and 180 out with only 3
> > terminals? Or am I reading this the wrong way?
>
> Thats a puzzler.  No.  Wait.  If the 'hot END' is not
> brought out, yeah.  That Works:
>
>                 )
>                 )<-------160_____
>         120_____)
>                 )
>                 )
>                 )
>                 )
>                 )
>                 )
>         0/N_____)_________0_______
>
> (if my sketch survives)
>
> One terminal at the tap, nominal 120 in.
> One for the wiper. 0 to 180 out.
> One for neutral/0 in and out.
>
> Needs to be checked by inspection and ohmmeter!
>
> > 2) Will the 033-6565 also handle 25 amps if kept to 120 volts?
>
> I'd think so.
>
> > 3) Anyone know a good place to get brushes for Staco variacs?
>
> dunno...
>
> best
> dwp
>

Hi dwp, Thad,
Yep. Checked that out. That's what's going on alright. The first terminal is
"common", the second terminal is the wiper and the third is tapped before
the end of the winding. The plastic terminal mount has 5 holes but only 3
have terminals. All I need to do is add a terminal to the end of the winding
that has none. Then I should be able to place it in parallel/series with
other variacs wired the same way to either increase current cabability at
120v or double the voltage rating.

Found another one from a guy I work with (he's a scrapper, got it for 8
bucks) but the first 1/3 of the windings were toast. Obviously it was hooked
up wrong. No idea what it is as far as the model but I was able to salvage
the brush, no obvious cracks or other flaws and it fits and works. Wish I
had a camera. Looks like someone dropped this thing from the top of the
grand canyon bouncing all the way down!