Power Factor...Zero-crossing

[lats]

Hi friends,

i'm trying to measure "power factor". On internet i read some articles from which i understand that time difference between the zero-crossings of Voltage and Current gives the power factor. But i'm not able to understand how to convert time interval value (lets say for example, time interval = 1 milli Seconds) into Power factor value. Can someone please explain it to me with some example.

Thanks.

 

[on1aag]

Hi Lats,

The ratio between the time difference of the zero crossings and the
period equals the ratio between the measured phase shift (phi) and
the maximum phase shift ( 2*pi radians or 360 deg or 400 grad ).
The rest is algebra . . .

φ = 2*Π*δt/T

cos φ = cos (2*Π*δt/T)

δt = 1 mS

cos φ = cos (2*Π*1*10E-3/20*10E-3) (50 Hz ; 20 mS)

cos φ = 0,951

Make shure that your calculator is set to the "right" degrees or radians.
Note that your calculator may lie a bit when checking extreme values
like 0 or Π/2 radians, rely on your own good judgement.

on1aag.

 

[engr_najam]

there r many other methods to calculate power factor e.g threee voltmetre method etc

 

[lats]

thanks on1aag for the help . i have this zero crossing detector ckt but this doesnt work . could u please provide me some appropraite daigram for zero crossing detection..