RE: [CAD_CAM_EDM_DRO] Transformer

> On the subject of transformers: Is there any way to determine what a

used transformer is able to do for you. Could you

>calculate current load, primary windings, secondary windings and various shunts

etc.? Or are they just garbage if you don't "know"

>which leads are which.

Well, a continuity tester will tell you which leads are just taps on a shared
winding. Within any particular winding, a sensitive ohmmeter can tell you the
relative turn counts between different taps (assuming that particular winding is
all the same wire size).
For determining ratios *between* windings (or for tapped windings with varying
wire gauges), I use a 60Hz low-voltage supply (i.e. from an audio signal
generator) to drive one winding, then measure the relative voltages.
Unfortunately none of this tells you the current rating of each winding. I seem
to recall, however, that there is a way of getting a ballpark kVA rating just by
weighing the transformer (core and coils only, no casing), on the assumption
that it was properly designed (optimal copper:iron ratio) in the first place.
Determining insulation breakdown voltage is also difficult.
-Kevin Martin