Re: [CAD_CAM_EDM_DRO] Transformer

"Kevin P. Martin" wrote:

> > 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.

An electrical engineer can figure all this out with relatively modest
instruments, knowing
nothing about the transformer, without even being able to SEE it. If
you can pull a cover
off and actually see the gauge of the wire and weigh the whole unit, you
have an
advantage. Measuring winding resistance with a DVM won't work. You
need a
milliohmmeter, or an impedance bridge. But, you can make educated
guesses if
you can see the wire gauge. Applying AC to the primary winding, you can
gauge
the turns ratio quite accurately. Applying known resistive loads (banks
of light
bulbs or power resistors) will allow you to measure voltage droop under
load.
Finally, I think there are some physical contants that cause all
transformers of the
same type, KVA rating and frequency to weigh in about the same. For dry

transformers of low voltage (about 24-440 volt windings) and 60 Hz, that
comes
out to about 1 KVA per 35 lbs (VERY roughly!)

Jon