Power Factor correction with CFL bulb question?

inetdog

Re: Power Factor correction with CFL bulb question?

JohnMassa wrote: »

Bill,

I stand corrected, A local 120VAC generator feeding a 25W CFL bulb with 0.5 power factor will pull 25W/0.5 = 50 VA. On a 120VDC generator or 120V battery the draw will be 25 VA. The AC generators are a better choice as many appliances cannot use DC.

It seems that multiple transformers and long transmission lines should cause more losses due to poor power factor than does an on site generator that doesn't have losses due to multiple transformers and long transmission lines. The main losses must be primarily in the generators?

John

John

The motive power source (engine of the generator, turbine at the POCO plant) only needs to deliver the watts used. But the current, and therefore the internal losses in the generator itself, depend on the A part of the VA.

BB.

Re: Power Factor correction with CFL bulb question?

Inetdog,

I know you deleted your post--But I believe you where correct--The office computer issue was a neutral return current problem and probably because the current spikes did not add up to "zero" in the neutral line for a Wye phase circuit (common for 120/208 VAC 3 phase power for an office park in California). 'Twas 35 years or so ago when I heard about the problem--stuff is a little fuzzier now.

-Bill

inetdog

Re: Power Factor correction with CFL bulb question?

BB. wrote: »

Inetdog,

I know you deleted your post--But I believe you where correct--The office computer issue was a neutral return current problem and probably because the current spikes did not add up to "zero" in the neutral line for a Wye phase circuit (common for 120/208 VAC 3 phase power for an office park in California). 'Twas 35 years or so ago when I heard about the problem--stuff is a little fuzzier now.

-Bill

I deleted it because it was a reply to a much earlier post, dropped in out of context at this part of thread.
But for those who are curious, here it is:

BB. wrote: »

PF issues have hit large companies before (decades ago, a local credit card processor using a whole building full of, then new, PC's kept burning out wiring and popping fuses--even though the the circuits were well under the power ratings--bad PF was the cause).

-Bill

The biggest problem was in office cubicles with built-in wiring. They were supplied with 3-phase power, and for PF=1 loads the neutral would never have to carry more current than any one of the hot lines. But with computer loads, the neutral was carrying three times as much current as the phase wires. Poof!
Beyond that, the peak phase currents were also more than the circuit was capable of even though the RMS values were OK.
And the final straw was that the current was in fact higher than you would expect from the wattage because of the poor PF.
Circuit breakers do not care specifically about the PF or the wattage, they just trip from current. (Usually RMS current, but.....)

ggunn

Re: Power Factor correction with CFL bulb question?

inetdog wrote: »

I deleted it because it was a reply to a much earlier post, dropped in out of context at this part of thread.
But for those who are curious, here it is:

When you say the cubicles were supplied with three phase power, do you mean that it was 208Y/120 with each computer powered phase to neutral on standard receptacles?

BB.

Re: Power Factor correction with CFL bulb question?

Yes, that is a very common power configuration for office parks in California (or at least, northern California). 120/208 VAC 3 phase Wye ("Y") connected (sometime open phase--just two transformers instead of three).

And 120/240 split phase for homes.

-Bill

inetdog

Re: Power Factor correction with CFL bulb question?

BB. wrote: »

Yes, that is a very common power configuration for office parks in California (or at least, northern California). 120/208 VAC 3 phase Wye ("Y") connected (sometime open phase--just two transformers instead of three).

And 120/240 split phase for homes.

-Bill

The fluorescent lights would then use the 208V, connecting line to line, and AC motors would actually use three phase wye or delta.

BB.

Re: Power Factor correction with CFL bulb question?

Actually, 277 VAC is also a very common voltage for industrial/florescent lighting... Phase to Neutral voltage for a 480 VAC Wye power system (480 VAC divided by srt(3)).

-Bill