Powerfactor measurement

Am working on a project that require accurate powerfactor measurement. Is the value of power factor calculated by ratio of realpower by apparent power accurate? As far as i came to know emonlib library measures rective power as product of the Root-Mean-Squared (RMS) average of the Voltage and the RMS average of the Current. Is this an accurate method to measure powerfactor ?

Thanks in advance for helping me out.

glyn.hudson's picture

Re: Powerfactor measurement

Use the voltage and current emon lib example, power in is calculated by dividing real power apparent power https://github.com/openenergymonitor/EmonLib/blob/master/examples/voltag...

Robert Wall's picture

Re: Powerfactor measurement

I think there is some confusion creeping in here.

EmonLib measures real power (W) as the average value of the product of instantaneous voltage and current. That is (in theory) absolutely accurate.

EmonLib also calculates the rms average of both voltage and current. Those too are (in theory) absolutely accurate. The product of those is Apparent Power (VA - volt-amperes).

The definition of power factor is the ratio of real power / apparent power.

EmonLib does not calculate reactive power (var - volt-amperes reactive). To do so requires the current to be multiplied by the voltage wave shifted by 90 °. Without that, there is no way to know whether the power factor is leading or lagging.

(I understand MartinR has done this with his PLL sketch but not published it.)


Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.