Using a transformer primary as a secondary

[John I. Jones]

Question - Does anyone have experience using a power transformer's
primary winding as a secondary? I received a mil surplus power
transformer from The Parts Connection that was advertised to have two
independent secondaries, but instead has only one with multiple taps. I
need two independent secondaries. It does have two primary windings that
are supposed to be connected in parallel for 115V use. I wonder if I can
use one of these primary windings as a 115V secondary - otherwise I need
to mail these behemoth transformers back to Canada.

I can think of two drawbacks: there may be more transfer of line garbage
to the second primary than to the legitimate secondary; and the VA rating
of the transformer will be reduced, I suppose in half. Anybody know of
any other drawbacks?

Thanks,

Jack Jones

[Don Borowski]

John I. Jones (te...@med.unc.edu) wrote:
: Question - Does anyone have experience using a power transformer's

I have done exactly what you are proposing with no problems. Secondary
voltage is reduced under load a bit due to resistance and leakage
inductance, so you might want to use the taps to adjust back up.

And yes, to be conservative, I would reduce the VA rating by half.

Donald Borowski WA6OMI Hewlett-Packard, Spokane Division
"Angels are able to fly because they take themselves so lightly."
-G.K. Chesterton