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In Reply to: RE: Your question is flawed posted by Russ57 on August 15, 2014 at 10:35:34
That is opposite of what I observe.
I have a 4' fluorescent tube near my desk.
As it warms, the PF rises.
Here are the 'cold' numbers:
House voltage=117.2 (Hot summer days drops the voltage from 118+)
I=0.34
P=31
VA=38
PF=0.81The 'advert' calls this a '40 watt tube'. I can't kick.
When it warms, the PF goes UP slightly.
As I understand it, YOUR formula is wrong. Watts = IE VA=watts x 1/PF
The 1/PF results in a number >1 which when multiplied by watts gives VA, which as I understand it is ALWAYS the larger of watts VS VA.I think the above is right:
PF is always <=1 and watts always <= VA P (in watts) = VA for resistive loads only.
Too much is never enough
Edits: 08/15/14Follow Ups:
I'll deal with the second part first.
As I understand it, YOUR formula is wrong. Watts = VA * PF
Watts does equal volt amps times power factor. That is a fact.
PF is always <=1 and watts always <= VA
The absolute value of power factor is less than or equal to one. Watts is less than or equal to volt amps. Volts time amps is apparent power. To know power factor you need to also know real power (measured watts).
Too much is never enough.
Totally depends:)
Your florescent lamp situation would need to be better defined. I am curious how you are arriving at a number for power factor. Do you have a watt meter designed for use on non linear loads?
It bears mentioning that a low power factor can be caused by reactive loads like inductors and capacitors. It can also be casued by non linear loads like a flourescent ballast or a rectifier in an amplifier. The latter are different and create harmonic distortion making it hard to state actual power factor. You might call the first a "displacement power factor" and the second a "distortion power factor".
I believe that PF is always <1 because it is the COS of the angle of displacement between voltage and current. That will ALWAYS be <1, and I don't think we need to apply Absolute Value to make it so.
Can there be a PF > 1 or a negative number? I know at a displacement of 90' NO power is delivered and at 91', you are back to essentially 1' of displacement.
OH! I'm sure I could get a better PF measure if I had the right instruments. I don't even have a true RMS DVM or a scope. I might have an ancient Simpson Senior Voltohmist out in the garage in storage, but haven't used it in a long time.
Too much is never enough
Power factor can range from negative 1 to positive 1. It is the ratio of real and apparent power. A purely resistive load would have a power factor of 1. A power factor of -1 would be something that is normally a load but is instead generating power power back into the source.
It is hard to communicate some concepts. Some things are vectors which can be added/multiplied but they are done differently. Other things are only true in certain conditions. When it is "displacment power factor only" the power factor is the cosine of the angle between the current and voltage sinusoid waveforms. When it is distortion all bets are off:)
It is even more confused by certain conventions such as calling leading/lagging power factor as +/-power factor. But rest assured, despite leading publications to the contray, there is such a thing as negative power and negative power factor.
You might find this link interesting....best I could do on a quick search.
http://www.cui.com/catalog/resource/power-factor.pdf
Power back into the source, eh? I'll run this thru the brain cell while keeping damping factor in mind. The perfect amp, with ZERO back resistance with the devices ON, should shunt all the back EMF to the driver which produced it in the first place, no?
I'll read the link tomorrow. I'm beat and expecting COMPANY which means I've work to do in preparation.
I'm even missing a meeting of my fellow planar enthusiasts who are having a small get-together tomorrow.
Too much is never enough
My formula, corrected, is correct.
And we said the SAME thing….about what is larger, VA or Watts.
Now, I use a Kill-A-Watt meter. Cheap, fast, easy and does NOT distinguish between displacement PF and Distortion PF. Accuracy? Who knows? Repeatability? Also who knows? It DOES seem reasonably repeatable when measuring the same device many times over several weeks.
I posted a paper from the EU about PF and its measure and the mandate for PFC on many devices. A few exceptions were made, but they talked a LOT about DPF (distortion PF).
My original question still stands, however, if you have a Non-Resistive load (PF <1) and you apply external PFC, do Watts to UP or does VA come DOWN? If VA comes down, you are ahead, If Watts goes UP, you might make your 'strain' on the power grid somewhat less, but are not really ahead from an actual power use viewpoint. In either case, the power grid is slightly better off.
And from our FWIW department, since you are both interested and knowledable, here is a link to a neat way to measure amplifier power. They measure at several fixed impedances AND from Inductive to Reactive at several points. The final 'graph' is very descriptive of an amps performance when things get weird. Not the audio graph link, but close enough.
Too much is never enough
if you have a Non-Resistive load (PF <1) and you apply external PFC, do Watts to UP or does VA come DOWN?
Volt amps goes down. Current is used more efficently. That is what the power company cares about and why they charge for poor power factor.
Ok, good.
Now, for those who can test such things, would such PFC effect the sound from the amp? Better? Worse? or perhaps just 'different'?
I think most audiophiles could care less about the electric bill, especially those fans of pure class 'a' or 'high bias' designs like Pass and a few others.
Too much is never enough
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