Re: [CAD_CAM_EDM_DRO] Sizing Rectifiers

Or to muddle up the situtation more you can have transformers with dual
secondaries on each primary winding.

With this you can get some really low ripple power out by connecting one set
of the secondaries delta and the other set Y. The input to the transformer
can be connected either delta or Y.

Each output is rectified with the 6 diode 3 phase bridge. The DC outputs of
each bridge are connected together (proper polarity please) and you get 12
pulse DC out instead of 6 pulse. This is because there is a 60 degree (1/2
of 120 degree) phase shift in the "odd" secondary.

Example delta input and the delta connected output are in phase. The Y (odd)
output windings on a delta primary is producing the sum of two of the input
windings.

Commonly used in high power X-Ray high voltage supplies but can also be used
for some low voltage high amp powersupplies without using a regulator.

High amp regulators are expensive relative to high amp diodes which you have
to have anyway.

Hugh

----- Original Message -----
From: <JanRwl@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Sunday, December 02, 2001 5:48 PM
Subject: Re: [CAD_CAM_EDM_DRO] Sizing Rectifiers


> In a message dated 30-Nov-01 23:33:38 Central Standard Time,
> ccq@... writes:
>
>
> > I've Never heard of a full wave _6_ diode bridge. I've seen plenty of 4
> > diode
> > bridges circuits, but never a 6. What do you do with the extras?
> >
> >
>
> Bill: Read again, THREE phases! That's three separate
> transformer-secondaries (six wires), connected in a "delta" configuration
> (three "terminals"). You connect TWO diodes to each "terminal", each
facing
> opposite directions, and the other ends of those, then, to the pos. and
neg.
> outputs. Repeat for all-three terminals. Two times three is SIX. Did I
do
> the math right? (I flunked Differential Equations!). This is "Full-Wave,
> Three Phase". It gives you a ripple-frequency six times higher than
> half-wave, single-phase, so, each "bump" is very short and of low
> potential-difference. Thus, the "filtering" is very easy, and the "raw DC
> out" is nearly equal to PEAK-AC voltage (1.414 x RMS, isn't it?).
>
> A three-phase rectifier, all else being equal, is more expensive than a
> "good, full-wave single-phase", but it gives a nicer, easier-to-regulate
> DC-out, it does! (Not worth that extra in many cases, but good when
> high-currents are needed, with decent regulation).
>
> Hope to have been usefully helpful! Jan Rowland, Troll
>
>
> [Non-text portions of this message have been removed]
>
>
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