[BC] AC Voltage Drop

[Jerry Mathis]

I've just done some on-line research via our friend Google. The technology
is very interesting, and very simple.  A 12-phase supply appears to require
two separate power transformers. I've seen examples of both connection
variations used (primaries delta and wye, or secondaries delta and wye).
Apparently there is a phase shift of about 30 degrees in a transformer,
depending on how it is connected. This is convenient since there is a 60
degree phase difference in 3-phase full wave rectifier output pulses. The
12-phase supply merely doubles the number of output pulses from the
rectifier, and has the added benefit of eliminating a lot of the harmonics,
AND improving the power factor of the supply.

I'd copy some of the stuff I found, but I'm not sure if I would be violating
anyone's copyright, and I really don't want to do that. Here's one link I
found, you can go there yourself if you're iinterested. If they've posted it
free and clear on the Internet, then looking at it can't be violating
someone's rights--can it?

http://www.powersupplyconsultants.com/INPUT%20POWER.pdf

--
Jerry Mathis

On 6/30/09, Milton R. Holladay Jr. <miltron at mindspring.com> wrote:
>
> IIRC, there is a wye secondary and a delta secondary which wind up being 60
> degrees different in phase such that, combined,  there are 12 pulses per
> cycle resulting from the 6 sets of rectifiers. The ripple is so low that no
> choke is required on the input of the fillter capacitor bank.
> I've heard them called 6 phase and 12 phase. Ftitz Bauer used it on his
> FB-5J and Collins adopted it also, as it worked especially well on AM xmtrs
> due to the low source impedance/very good regulation  of the non-choke
> input
> filter power supply accommodating the pulsating load of an AM xmtr.
> Perhaps Richard can probide more tidbits................
> M
>