Date: Tue, 28 Oct 2025 19:45:52 -0700
From: Michael Tope <W4EF@dellroy.com>
To: amps@contesting.com
Subject: Re: [Amps] Paralleling plate xfmrs.
>Yeah, based on the numerous examples you cite, Jim, and the LTspice
>simulations, I am convinced that paralleling can work, but that there
>will always be at least some current imbalance. Whether or not that
>imbalance is significant depends on the specific parameters of the
>transformers involved (e.g. secondary voltage matching, winding
>resistance, etc) and how much imbalance can be tolerated.
>Good discussion thread.
>73, Mike W4EF...........
Sure there may well be some current imbalance, but unless the 2 x plate
xfmrs are both beyond maxed out, you will never notice it. And even
maxed out, we still couldn't notice it...at least temp wise.
One other config was tried, and that was using 2 x identical dahl xfmrs,
but one had a 5200 max tap...and the 2nd one had a 5400 max tap. The
solution was to run the 5200 vac xfmr on it's 230 vac pri tap...... while
the 5400 vac xfmr used it's 240 vac pri tap. With 240 vac applied to
both primaries in parallel, the 5200 vac xmfr is now (5200/230) x 240 =
5426 vac
So only a 26 volt difference between the secondaries....and a 36 vdc
difference once rectified. 7672 vs 7636. 7636 / 7672 = .995 That's a
.5% difference = dick. Again, they ran fine in that config.
Myself, my 1st choice is a single (bigger) xfmr. Latest supply uses a
single dahl xfmr, but with TWO identical FWB assys' in parallel. I had a
spare FWB assy, so instead of putting it on the shelf, it was instead
paralleled with the 1st assy.
The filter assy for it is a bit bizarre, it consists of a C-L-C setup. The
choke is in series with the B+, but insulated from the chassis...via 4 x
massive glastics. (tnx Shane). I installed a HD Kilovac SPST-NC relay,
with contacts wired to the choke terminals...and also a hb adjustable spark
gap across the choke terminals. It can be used in the C-L-C config or a
C + C config with choke shunted out. It's overkill, but buddy across town
had the recent vintage 127 lb Dahl, 4H ( 3 amp CCS) choke sitting in
his heated basement...so I sweet talked him out of it.
All this stuff just barely fits into the new Hammond rack cabinet.
Jim VE7RF
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|