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Re: Variac Parallel Choke Questions



In a message dated 2/11/00 7:07:07 PM !!!First Boot!!!, tesla-at-pupman-dot-com 
writes:

<< Original Poster: Eric Leighton <ELeighton-at-portdiscovery-dot-org> 
 
 I have two 10A Powerstats that I plan to run in parallel.
 
 Mechanicals: 
 
 Regarding the common shaft, the list consensus (thanks folks) seems to be
 that any material of the right size and sturdyness will suit, as long as
 it's electrically isolated, so you don't form a closed electrical loop
 around the core (thanks Terry).  I'm going to go with thick walled stainless
 tubing, simply because I have it sitting here on my desk.  
 
 Electricals:
 
 Regarding the electrical connections, a search of the archives reveals that
 some list members have had success just adjusting the rotor to the same
 voltage, without any choke.  Any reports of failures or hot-running using
 this kind of setup would certainly be appreciated, since this option
 certainly is the easiest, if it works ok. 
  >>
- snip -

Eric,

I have a pair of 10 amp 120 volt variacs that I used for several months when 
I was running four 12 kv 30 ma transformers in parallel.  I made a mounting 
assembly for the two variacs out of 1/8" steel plate welded together and 
connected them together with an aluminum shaft.  Then I lined up the rotors 
and tightened the set screws.  Connect them in parallel and have at it.  You 
could measure the voltage differential between the two common (wiper) 
terminals to see how close they are tracking.  I never did have any problems 
with them getting hot.  However, if I would have had some heavy, low loss 
chokes handy, I probably would have used them.

Ed Sonderman