In article ,
keith wrote:
On Sun, 11 Sep 2005 02:08:43 +0000, David Combs wrote:

....

Of course there's the "rms" stuff, trying to
get an average value of a sine-wave.

Not average. When Volts is multiplied by amps (power) there is a squared
term in there. RMS == Root Means Square (root of the mean square), so
when you calculate power, the squared term is taken into account.
Yes, I now recall that.

Average
voltage isn't all that useful; the average for sine wave is zero. ;-)
Indeed!

The pf, I recall from *ages* (decades) ago, had something to do with the
voltage and current "waves" getting out of sync with each other, due to
a coil or a capacitor (one shifting in one direction, one in the other).

Or a non-linear load adding harmonic content to the waveforms.

....
....
How do you get a substantial pf for a fluorscent (sp?) light?

The fluorescent is a non-linear load. It chops the current waveform,
adding harmonics to it.

The harmonics being like the terms in a (*very* dimly recalled) fourier series
or transform that sum up to approximate the chopping-caused square or
impulse or whatever waveform it is?

As I asked in my other reply, do you know offhand any
good sites that cover this stuff (with drawings, too)?

The above formula isn't very useful in this case.

So, what is?

(Huge electric motor, I understand how.)

A "huge electric motor" should have a PF very close to one if it's heavily
loaded. If it's creating no mechanical work, then it will have a worse
PF.

Jeez, on the surface, that sounds like the *opposite*, maybe,
of what one would expect???

Maybe you could say some more?

(I knew way back then that going for a double-E would be
way over my ability!)


And a pf for an incandescent light, that would involve no phase shift at
all?

The phase shift will be small, but it will only conduct current during
part of the cycle, chpping the current waveform. Since the current isn't
being used during the entire waveform, the power uring this part of the
cycle isn't useful.

Wow... Maybe you could say a bit more about that!

(This stuff is NOT simple!)


Thanks to all for a fascinating look into the dark.

David