Power factor measurement

[Sajeesh]

Hi,

How to calculate Power factor in FPGA?

NI 9242,NI 9246 ,cRIO9066 are used in project.

NI 9246 current measurement module is synchronised with NI 9242 voltage measurement module.

Rate of data acquisition is 50Ks/s for both NI 9242 & NI 9246

Single phase (230 V AC,50 Hz) is to be measured.

1.Current RMS  Using DC and RMS measurement.vi  in FPGA  (1000 number of measurement samples,no windowing).

2.Voltage RMS  Using DC and RMS measurement.vi  in FPGA  (1000 number of measurement samples,no windowing).

3.Apparent power=Voltage RMS*Current RMS.

4.Real Power is calculated by Mean of 1000 number of measurement samples (V instant.*I Instant.)

5.Power factor=Real Power/Apparent power

the load is a tungsten filament bulb ( 60W)

the power factor varies between 0.9999 and1.00022,why there is fluctuation in calculated power factor?

[paul_cardinale]

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@Sajeesh wrote:

Hi,

How to calculate Power factor in FPGA?

NI 9242,NI 9246 ,cRIO9066 are used in project.

NI 9246 current measurement module is synchronised with NI 9242 voltage measurement module.

Rate of data acquisition is 50Ks/s for both NI 9242 & NI 9246

Single phase (230 V AC,50 Hz) is to be measured.

1.Current RMS  Using DC and RMS measurement.vi  in FPGA  (1000 number of measurement samples,no windowing).

2.Voltage RMS  Using DC and RMS measurement.vi  in FPGA  (1000 number of measurement samples,no windowing).

3.Apparent power=Voltage RMS*Current RMS.

4.Real Power is calculated by Mean of 1000 number of measurement samples (V instant.*I Instant.)

5.Power factor=Real Power/Apparent power

the load is a tungsten filament bulb ( 60W)

the power factor varies between 0.9999 and1.00022,why there is fluctuation in calculated power factor?

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1. Measurements aren't perfect (neither in magnitude nor time).

2. Temporal aliasing.

[Sajeesh]

hi

Thanks for reply

In the previous case every calculation was done in FXP

When FXP is converted to SGL data type there is much improvement. Hope it would be due to rounding/overflow of data.

First chart is in FXP

Second chart in SGL