RJT>Greg Mayman wrote in a message to Steve Asher:

RJT> GM> This is repeated for each of the three phases to give six outputs 
RJT> GM> whose relative phases are at 15, 105, 135, 225, 255 and 345 
RJT> GM> degrees.

RJT> GM> The whole process is then duplicated to give six more outputs that
RJT> GM> are the inverse of the above, that is shifted by 180 degrees, so 
RJT> GM> we now have outputs at 195, 285, 315, 45, 75 and 165 degrees.

RJT> GM> So the output from the transformer is 12 separate phases, at phase
RJT> GM> intervals of 30 degrees.

RJT> GM> Feeding this into a 12 phase bridge rectifier -- 48 diodes!!! --
RJT> GM> gives an output with peak-to-peak ripple of only 0.86% WITHOUT THE
RJT> GM> NEED FOR ANY FILTERING!!!

RJT> GM> A really ingenious design :-))))

RJT>I used to see stuff like this in some books,  and figure that I'd *never* have
RJT>to deal with stuff like that.  But not necessarily...

RJT> GM> Something like this would be ideal for feeding a DC transmission
RJT> GM> line.

RJT>That's not the only place it'd be useful.

RJT> GM> I've never worked out what the input current waveform would be. It
RJT> GM> would be interesting to know how far it departs from a sine curve.

RJT>I'll tell you where such stuff is used now!  In automotive applications...

RJT>The older alternator that I have in my truck probably has six diodes in it, 
RJT>that was a pretty common setup.  There are four connections to it,  the ground
RJT>connection,  the main output terminal,  and two field terminals which are
RJT>modulated to give the desired output.  I have no idea what's in the
ones in the
RJT>other two vehicles here,  though they're considerably newer in design.  I have
RJT>heard of some General Motors units that have up to 12 or more phases,  though.

In looking at the factory shop manual for my 92 Chevy PU the
alternator design is identical to those of the very first
alternators - with respect to the number of diodes. I
haven't anything later to reference.

Jay

RJT>I'll bet that the prevalence of lots of computer logic,  and other solid-state
RJT>parts in newer vehicles has something to do with this.  That voltage *has* to
RJT>stay up closer to nominal,  and the battery can't be counted on to keep it up
RJT>there,  even with higher cranking-amp ratings,  when you're starting.

RJT>--- 
                                                      

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