derive power factor from neutral current

[drew.kramer]

Is it possible to calculate the power factor if you know the neutral current? It seems like you should be able to calculate the theoretical neutral current, compare to actual and derive the power factor. Here's some actual measurements:

A=54
B=43
C=58
N=25

Ncalc=13.45 from sqrt(A*A+B*B+C*C-A*B-A*C-B*C)
Ndiff=11.55

Is my power factor:
1 - Ndiff / (A+B+C) = 0.92

It seems too simple...

-drew

 

[ron]

Re: derive power factor from neutral current

The power factor is a value that identifies the relative phase angle of voltage and current. Your calculation does not include voltage.
If the load was at steady state, you can measure wattage, voltage and current, then you could calculate the power factor from measurements. W=IV*PF*1.73 for 3 phase

 

[charlie b]

Re: derive power factor from neutral current

Originally posted by drew.kramer: Is it possible to calculate the power factor if you know the neutral current?

Sorry, but no. I strongly suspect that the difference between the calculated and measured neutral currents is the result of harmonics. In order to calculate power factor, you need to know the value of some additional factor. Ron?s formula would work, if you were able to measure the items he listed. You could also calculate power factor from resistance and reactance values, if you measure them. As Ron says, knowing only current will not be enough.

 

[pwhite]

Re: derive power factor from neutral current

the power factor is the cosine of the phase angle between the voltage and current. as already pointed out, there are other things to consider.