From: pallison49@gmail.com   
      
   Bob Engelhardt wrote:   
   >   
   > I was looking for a 120-120 isolation transformer on eBay and I kept   
   > finding 120-240/480 transformers.  There are 2 secondaries on these   
   > (connect in parallel or series).  It occurred to me that I could use one   
   > of these as a 120-120 by using one secondary as input and the other   
   > secondary as output.  I know that this is theoretically possible, but   
   > are there practical reasons why it wouldn't work?   
   >   
      
   ** A 120-120 transformer does not have equal windings, the secondary has   
   additional turns to allow for the regulation factor of the unit. Might be   
   anywhere from 4 to 20% extra turns on the output side.   
      
   Also, a properly made 120-120 would also have good insulation between the two   
   windings rather than them being overlaid or wound bifilar.   
      
   Another factor is magnetising current - transformer primaries are sized to   
   allow for the extra current but secondaries are not since there is none.   
      
      
      
   > Also: if one of these 120-240/480 transformers is rated 500VA, that   
   > means 1 amp on the secondary, right?  I.e., 1A at 480v.   
   >   
   >   
      
   ** Yep - the VA rating describes what rms current x voltage available from the   
   secondary.   
      
      
   ....  Phil   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)