[sdiy] Polyphase transformers

[cheater cheater]

Hi guys,
thanks for the replies :-)

On Sun, Nov 21, 2010 at 12:32, Richie Burnett
<rburnett at richieburnett.co.uk> wrote:
> Polyphase transformers just perform vector additions of the waveforms
> applied to them...

ok, I understand you mean when the waveforms are sinusoids? I don't
know "vector addition of waveforms" other than when you take a vector
with the phase of the sinusoid and the magnitude being the amplitude
and add them like that. Is there some form of generalization to
arbitrary waveforms? If so, how does it look? Got me curious there :-)

> So they can be used to play tricks with the relative
> phases of 3-phase sinusoidal voltages applied to them in power distribution
> systems.  (E.g. Look up the "24-pulse rectifier" for an example of how
> something called a "star-delta transformer" is used to generate 3 additional
> phases with offsets of 30 degrees from each of the existing 3-phase supply
> line voltages.)

I have looked it up but have been confronted with super-technical
stuff that went way over my head :-) I've seen star-delta transformers
in tri-phase generators, though, I think? Am I right to think they're
the same thing you are referring to?

> Unfortunately a polyphase transformer doesn't impart any time delay to
> signals passing through it like you would need to implement something like
> an audio phaser.  Effectively it is just a mixer performing vector addition
> of the multiple input phases.

Yes, but it does impart phase delay, doesn't it? And phase delay is
just frequency-dependent time delay. I've experimented a bit with
phase-delay and it sounds just like a normal "opto" phaser would - I
can only recommend that - a bbd-based phaser can't compete

> 3-phase transformers also tend to weigh 300lbs and need a flatbed truck to
> move, so probably not ideal for Synth DIY !?!?!?

Haha, yes, fully aware of that! However, an inclined person might wind
their own low-voltage transformer...

Thanks,
D.