Hi Gang,

I have a large and heavy power supply transformer
that is part of a high current power supply project
that was featured in 73 magazine back in 1973. It
was started by a ham radio operator and was never
finished. I am going to finish it, if I can. I am
trying to identify the transformer leads. This is
for a 12 volt, 40 to 60 amp output. Here are the markings:

This transformer was made by ADC and is marked 541-010 REV H.
There is a marking on it that says 3-19470 and what I think
is a date code of 7438. There are terminal connections on one
side that are numbered 1 - 6. On the other side the connections
are numbered 7 - 14. I need to know the connection scheme for
this transformer so I can put it to use. I contacted who I
thought was the manufacturer "ADC" for information, and that
did not help.

I don't have the issue of 73 magazine, and I don't even know
if this is the same transformer that may have been part of the
construction article. I can take pictures and post them if that
might help.

Anybody have any ideas?

Thanks a lot.

Mike

Anybody have any ideas?

Ohm out the windings. Figure out which ones are center taps for the
secondary or input voltage selects on the primary. (It may have two
independent secondary and/or primary windings if center-tapped out and
intended to work on both 120 and 240 VAC).

The lowest resistance winding is the high-current secondary. The
primary must be one of the other windings (if you're lucky the only
other winding is the primary!)

Tim.

_Usually_ the primary, or one of the primaries, begins at pin 1. If
you get two windings that measure about the same resistance, and its a
few ohms, it's probably a split primary. You can insure that you get
the phasing right if you connect the two windings in series, and apply
120V to just one of the two. Then if you get about zero volts across
the whole series connection, you have the two connected counter-phase,
like dotted ends connected together. Try the other polarity for one
winding and see if you get 2* the applied voltage across the whole
series connected primary, which would be in phase (dotted end of one to
the undotted end of the other.

It's helpful if you have a variac (NOT a lamp-dimmer triac) so you can
run the voltage up slowly. An alternative that works nicely is an
incandescent light bulb in series with the 120V supply. If the series
lamp, 100 watts or so, lights very dimly or not visibly at all, with
nearly all the voltage across the transformer winding, you've almost
certainly got it connected to the primary. The light bulb will keep
you from blowing breakers or fuses. If the transformer has an internal
short or you're hooked to the secondary (or if you short the secondary
or put a heavy load on it), the lamp will light much more brightly.

Of course, be careful. The primary side can give painful shocks,
possibly leathal ones. And the secondary side can deliver enough
current to make pieces of metal very hot.

Cheers,
Tom

It's helpful if you have a variac (NOT a lamp-dimmer triac) so you can
run the voltage up slowly. An alternative that works nicely is an
incandescent light bulb in series with the 120V supply. If the series
lamp, 100 watts or so, lights very dimly or not visibly at all, with
nearly all the voltage across the transformer winding, you've almost
certainly got it connected to the primary. The light bulb will keep
you from blowing breakers or fuses. If the transformer has an internal
short or you're hooked to the secondary (or if you short the secondary
or put a heavy load on it), the lamp will light much more brightly.
==========================
To check the windings of any transformer I always use another mains
transformer with a low secondary winding output of say 12 or 6 volts. I
connect the low voltage output to one of the windings of the 'mystery'
transformer and with a DVM check the voltages on the other windings .This
provides the winding ratios ,from which the actual operating voltages can be
derived ,with additional information from winding resistances.

To check the current ratings of a secondary winding I increase the load on
that winding until the output voltage is 95% of the 'no load' voltage . The
corresponding current is the safe maximum current to flow through the
winding .
Depending on the transformer's output voltage ,I use car bulbs or a lenght
of fencing wire (iron) in a bucket with water for low voltages , light
bulbs (parallel and/or in series ) for voltages up to 500 V or even higher
(be careful).

Frank GM0CSZ / KN6WH

Additional thought: you may be able to see wires connected to the
terminals. If so, it should be obvious which windings are the higher
current ones and which are the higher voltage ones.

It's also possible to make estimates of the current rating of the
windings from the wire size.

Cheers,
Tom