XPost: sci.electronics.design, sci.electronics.equipment, sci.el   
   ctronics.repair   
   XPost: rec.crafts.metalworking, rec.woodworking   
   From: invalid@invalid.invalid   
      
   Joerg wrote:   
   > DaveC wrote:   
   >> Imagine you are asked to install a used buck-boost transformer. Imagine you   
   >> could normally do this in a few minutes. Except if the leads were cut short   
   >> such that identifying characters on the leads' insulation were missing.   
   >>   
   >> Identifying 2 leads belonging to any one winding is straightforward ohm   
   meter   
   >> work. Maybe use of a ESR meter might help separate the X windings from the H   
   >> windings?. But identifying which specific winding is which and which end is   
   >> which­­not so straightforward. For me.   
   >>   
   >> How would you go about identifying the windings? Maybe use a Variac to input   
   >> voltage to each of the windings then measure the output of the others? What   
   >> outputs should I expect at, for example, the H3/H4 winding with a voltage on   
   >> H1/H2 winding? How to identify backward connection of a winding?   
   >>   
   >> Are the two H windings identical? The two X windings?   
   >>   
   >> Suggestions welcome.   
   >>   
   >> This is a 208 -> 230 (ie, 12 & 24 v buck-boost voltage) single-phase   
   >> autotransformer in N. America.   
   >>   
   >> Thanks.   
   >>   
   >   
   > Assuming you have ohmed them all out and thus know how many windings   
   > there are and how many taps each has:   
   >   
   > Hook a function generator to one winding (any winding), best one that   
   > has no taps. Measure the amplitude you get at a 10kHz or so. Most   
   > multimeters will do that, or a scope. Now measure the amplitude at all   
   > others. That gives you roughly the turns ratios.   
   >   
   > Now you normally also need to know which one is the helper winding   
   > because that sits close to the primary in the stack and should under no   
   > circumstance be mixed up with any of the scondaries. From your previous   
   > measurement you know which one is the primary (on 120VAC to low DC   
   > supplies that's the one with the highest number of turns). Hook that to   
   > one side of the capacitance terminal on your multimeter. Keep leads as   
   > short as possible. Measure capacitance to all others. Usually the   
   > highest capacitance indicates which windings are closest to each other.   
   >   
      
   Oops, if yours is not an "electronic transformer" disregard the above.   
   But then it's not really buck/boost.   
      
   --   
   Regards, Joerg   
      
   http://www.analogconsultants.com/   
      
   --- SoupGate-Win32 v1.05   
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