Power Factor info

[kbowers]

I must investigate about power factors and I do not know anything about them. Could someone give me a basic explanation about the causes and defintions and all things relevent to a power factor. Also I am looking of info on voltage disrtotions and power distortions casued my high voltage lasers. Or links to helpful site would be appreciated.

 

[tgott]

Power factor is defined as the cosine of the angle between the voltage and current in a circuit. In a purely resistive circuit the voltage and current are in phase, angle equals 0 degrees, so p.f. = cosine 0 = 1 In a purely capacitive circuit the current leads the voltage by 90 degrees, so p.f.= cosine 90 = 0. And in a purely inductive circuit, the current lags the voltage by 90 degrees, so p.f. = cosine -90 = 0. Most circuits have a combination of inductance and capacitance, and so the angle is usually between 0 and -90. E.g. if current lags voltage by 20 degrees, then p.f.= cosine -20 = .94. The closer the p.f. is to 1 the better because more of the power is able to do real work (watts), as opposed to "reactive" work (vars). Any good electrical engineering AC circuits book should be able to expand on this.

 

[jbartos]

Suggestion: The power factor for pure sinusoidal waveform of the fundamental frequency is:
PF=Pwatts/Sva=Pwatts/(Pwatts**2 + Qvars**2)**0.5
If the current and or voltage waveform(s) are/is distorted by harmonics, then more complex equation(s) for the power factor shall be used.
This topic has been dealt with in this Forum already. It is possible to search for it in Advanced Search. E.g. enter:
Power Factor Correction
Displacement Power Factor

 

[jbartos]

Suggestion: Visit

http://www.microconsultants.com/tips/pwrfact/pfarticl.htm

http://www.pscad.com/main/downloads/pscad_news/PDF/psnews16.pdf

etc. for more info

 

[Marke]

follow the link at

http://www.lmphotoncs.com

for a paper on power factor. Mark Empson

http://www.lmphotonics.com

 

[busbar]

thread248-20845
thread238-16805
thread248-19761
thread238-8873
thread237-1802
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thread238-17268
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thread238-10475
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thread248-2227
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thread238-225

http://www.eng-tips.com/search.cfm?...ID=58262001&CFTOKEN=1790242&requesttimeout=75

...well, you get the idea

 

[kbowers]

Thank you all for your help.

 

[electricpete]

I'm not familiar with lasers but it seems possible that the associated electronics represent a non-linear load which draws current harmonics, even in the presence of an otherwsie sinusoidal voltage source. Current distortion also has an impact on power factor.

In the presence of sinusoidal voltage supply (a helpful approximatio), Overall PF can be expressed as the product of a displacement power factor (cosine of displacement angle between the fundamental voltage and current) and a distortion power factor (distorion power factor is the ratio of the rms quantities I1/Itot where Itot is rms of total current waveform including fundamental and harmonics)