Thanks to you and Dave for this. I know we've veered way off topic
and much of this is so technical it can be a little hard to digest
unless you happen to have some background in this area, but you've
both done a pretty good job of explaining it in a way those of us less
knowledgeable, like myself, might understand (and that can't be an
easy task).

One of the things that continues to amaze me about this forum (and
others like it) is the amount of knowledge out there and, moreover,
the willingness to help others. I've certainly benefited from this
myself, many times over, both in practical, everyday matters and some
of these more theoretical concerns as well.

Cheers,
Paul

On 14 Feb 2007 07:37:49 -0800, "dpb" wrote:

The "third harmonic" thing is the result of chopping a DC supply, and
not the same as a chopped AC supply. I'm sure there is some 3rd-
harmonic content, but with a chopped sine the theoretical waveform
won't be the "all odd harmonics in 1/N magnitude" of the chopped DC.
OTTOMH I don't recall the characteristics of the transform for the
chopped sinusoidal case and was/am too lazy to get up and look for it
(and definitely too lazy to work it out ), but it's different--just
how different was what I was hemming and hawing about. It is, of
course, dependent on the phase angle as well as the discontinuity
changes characeristics as the chopping point moves through the cycle.
Actually, as I think about it, while the zero-switching is
advantageous from the standpoint of switching small currents, it is
the steepest gradient of voltage change w/ time, so in fact, the worst
from the standpoint of generating harmonics. But, the fact that it
isn't a square wave means it isn't the odd-harmonics only case.