Re: Ganging 1256D's

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

Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-uswest-dot-net>" <bert.hickman-at-aquila-dot-net>

Richard,

You want to connect them in parallel. You can then switch the input to
either a 120 or 240 volt source depending upon the maximum output
voltage desired. That way, you'll get 2X the current capacity at either
voltage. 

Although you can probably live without it, a center-tapped high current
balancing choke can be used to prevent circulating currents from
flowing  between the two variac outputs in case there's a slight voltage
imbalance between them. 

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-net
Web Site: http://www.teslamania-dot-com
  

Tesla list wrote:
> 
> Original poster: "Richard Wayne Wall by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <rwall-at-ix-dot-netcom-dot-com>
> 
> 3/11/01
> 
> I have recently added a second Powerstat 1256D variac to my power cabinet.
> They are identical 0-280vac, 28 amp, 7.8 kw single phase.  I have ganged
> them together and wish to increase the power to 15.6 kw at 56 amps.  I also
> wish the capability to just use one leg for occasional 0-140 vac output.
> 
> My question is should I hook them up in parallel or in series with one hot
> leg going to each variac?  Seems if in series each will still be limited to
> 28 amps.
> 
> RWW