Transformer identification

[harry bissell]

Its probably a good idea to use a 110 / 6.3 volt filament transformer at the
Variac output... It will be much easier to regulate, have much less chance of
frying a winding by accident... and will give you the isolation to stop you
from being an unintended secondary... :^) Harry

Grant Richter wrote:

> As I recall an article in Popular Electronics from the 70s...
>
> A Variac is a variable output transformer that can go from 0-130 VAC.
> The idea is to put a AC current meter and AC voltmeter on the output
> of the Variac. You can then set the current and voltage to some reasonable
> power level (like 100 milliwatts). Since most power transformers will take
> a
> tenth of a watt into either winding without blowing up.
>
> You can then measure the voltage out of the other winding and get
> the turns ratio. Even if you get it backwards, the power level
> is limited. Bear in mind that most variable transformers are not
> isolated from line hot, so treat the whole circuit like it's hot.
>
> ----------
> > From: J. Larry Hendry <jlarryh at iquest.net>
> > To: Synth-DIY <synth-diy at mailhost.bpa.nl>
> > Subject: Re: Transformer identification
> > Date: Monday, August 09, 1999 7:05 PM
> >
> > > From: Tim Nowaczyk <zimage at cs.wisc.edu>
> > >      I found a few old TV transformers and I was wondering if there is
> an
> > > easy way of determining the values without destroying them.  On has
> about
> > > seven or ten wires comming out of it and is very large, so simply
> putting
> > > a voltage across some wires and testing the secondaries is out of the
> > > question.
> >
> > (and quite dangerous)
> >
> > But, that brings up an intersting question.  Is there anyway to quickly
> > check the ratio of such a transformer from winding to winding.  We have a
> > simple-to-use tester at work (but probably not cheap) that we use to
> verify
> > the ratio of large power transformers (as part of a series of testing).
> > Anybody know how these work?  Knowing the ratios of a transformer and
> > something about the original application could easily lead one to the
> > appropriate connections and voltages.
> >
> > Larry H