Electrical power suit negative values

[kunal1261]

I'm using 9225 cards for my voltage and current acquisition. Both these values and their graph is okay.but when im trying to calculate power values using electrical power suit, it shows negative values. Daq config. is , acquisition mode: N samples, samples to read: 100 and rate : 1kHz

[James_McN]

Can you post some images/data/code? It makes it much easier to make suggestions.

The only thing I can think is it is trying to show generation rather than consumption or vice versa.

Cheers,

James

[kunal1261]

RMS values of my current and voltage is correct. But active power and power factor is showing random values. Is it due to any hardware problem like ground? Or is there any particular daq sampling settings that r needed?. Please help me out here.
Thank you

[James_McN]

Hi Kunal,

You need to share some code or images to be helped properly, we can't guess from the symptoms alone.

The symptoms may point to a phase measurement issues. You would need to see that the modules are properly synchronised otherwise your phases will be out and that means so will your power factor.

Cheers,

James

[kunal1261]

Current is converted to voltage using register for data acquisition. I've taken both values on NI9205. RMS values of both are correct. but power factor and rms values keep varying from negative value to position value continuously in some range. please suggest any possible way out. 

[James_McN]

Do you see any change on the graphs when this happens? Do the graphs look correct otherwise?

The 9205 is a multiplexed module so it will introduce some phase error but it should be constant (4uS between each channel) and doesn't explain what you are seeing.

I would try imediately converting the dynamic data to an array of waveforms. The power subVIs aren't designed for the dynamic data types and while it should work out the correct conversion, you never know!

Also try removing the filters. These can have impacts in the phases. Again though it should be constant but if you try removing it and it fixes the problem then at least you know it is related to those.