"--" wrote:
apparently you have not seen the equations governing reactance to make the
statements you do about

Your descriptions apply to *your* comments, not mine!

deh said
the "AC" equations are rigorous, and
apply equally well to your one-voltage DC when the frequency drops to zero-
the reactance term of the changing magnitude [current equation] then goes to zero.

fld said
That is an hilarious idea! If the magnitude is zero all the way
around... we aren't talking about AC or DC... maybe about
blown breakers or taking a coffee break, but not about current.

nor have you ever designed a switch carrying power loads, to say that in
non-DC rated switches, arc quenching does not rely on current reversal.
Or to ground fault design, I might add.

So your one single point of exposure defines the entire field?

I don't think so at all. You are trying to say that specific
instance is the general case. I was saying that it isn't, and
that the general case is *much* larger.

deh said
Because the reactance equations only apply to varying magnitude, and they do
not apply to reversing direction.

fld said
Then why would we be concerned at all about this reversing
direction, and give it a specific name and have a whole separate
field of study for it? Sounds like we need to be concerned with
varying magnitude, *not* with reversing direction. (Which is
what I've been saying...)


As I said, your position works only if you are in one corner of one part of
all electrical phenomena, and if you use technicians tools rather than
engineers and scientists tools.

That describes *your* position very well!

You will just have to live with what the big boys in academia say is
alternating current - they are not going to change the widely applicable
proven rigorous for a circuit design technician's philosophical musings.

Actually, getting too deep into either one, or into any single
field in either one, is what causes these assumptions like
yours, that specific instances are the entire general case.

One of the problems with academia, for example, is this
specialization. Whereas someone who works in the field runs
into whatever each project coughs up. The exposure is
significantly greater. And no that does not mean that academics
is bad, wrong, poor, unnecessary, less that useful or any other
silly thing you are likely to try twisting it into. It does
mean that it necessarily, for any one individual, has a narrower
scope, and people with field experience have a broader view,
generally (which also often lacks as much depth too). Both are
necessary.

"Floyd L. Davidson" wrote:
Bad example. That does *not* require a direction reversal. All
it requires is understanding that it is relative to the static
state.

you really don't know much about power switches, do you?

Well, I certainly do lack depth in that particular subject! But
knowing about power switches doesn't define understanding AC vs
DC, even if that is your field of expertise. In fact, it might
be the cause of your confusion.

Power switches may in fact operate at the moment of direction
reversal, but that is merely one specific example of the broader
"relative to the static state" general description that I gave.
The switch can happen at any time there is no current flow (or
rather, when the phase angle and rate of change is appropriate)
across the "contacts". But that can be at some DC potential
which is equal on both sides of the switch, or at a zero
voltage, either of which is *not* at a current direction
reversal. Maybe those circumstances don't happen with AC
distribution power switching, but they most certainly do in
other fields.

The requirement is *not* that a direction reversal be taking
place. That is just a collateral circumstance that happens to
exist in AC power distribution systems at the same time the
necessary phase relationship exists.

The very same general principle is used in video switching...
except not at a time when there is any change in current
direction!

--
Floyd L. Davidson http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)