RE: How are 240 VAC variacs made?

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

Original poster: "John H. Couture" <couturejh-at-mgte-dot-com> 


Finn -

Have you actually tested this wiring setup? I believe you will not get the
280 volts with the setup you have shown which is a short circuit across the
output. If you move the two wipers to the other ends of the windings you
will get a lower voltage. If the 240 volt input is grounded there will also
be differences in the voltage vectors to ground. However, I do not have two
variacs to make any tests.

John Couture

--------------------------------


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Sunday, February 29, 2004 1:38 PM
To: tesla-at-pupman-dot-com
Subject: Re: How are 240 VAC variacs made?


Original poster: Finn Hammer <f-h-at-c.dk>



Tesla list wrote:
 >Original poster: "Hydrogen18" <hydrogen18-at-hydrogen18-dot-com>
 >How are 240 VAC variacs made? Since the feed you get from your pole pig is
 >240 VAC center tap, are they really 2 120 VAC variacs with linked shafts
and
 >aligned rotor contacts? I dont see how you get it to work if it wasnt
 >because the rotor contact would be a potential to either side of the line
 >but would really be pulling from only one half on the transformer and
 >essentially feeding it with 120 VAC although it would be able to deliver
 >0-240 VAC.
 >---Eric
 >

Eric

There are 2 popular ways to make these variac`s, one for the dumpster
diver, another for the pro.

The pro just orders a 240/280volts variac, which has enough windings to
sustain the voltage.

The scrounger hauls 2 120 volts variacs home and connects them like this:

             +----------9 <----------------
             |          9            ^
             |          9            |
             |          9            |
             |          9            |
             |          9          0-280V
      -------)----------9            |
     ^       |          9            |
     |       |          9            |
     |       |                       v
     |       +----------9 <-----------------
    240V                9
     |                  9
     |                  9
     |                  9
     v                  9
     -------------------9
                        9
                        9

The "9`s" are the windings.

If morale is high, he connects them on the same shaft, but this is not
necessary.


Cheers, Finn Hammer