EPM palette active power measurement

[JLE]

Hi all,

For a series of power measurements with Labview I am using the NI provided EPM palette for the basic calculations such as RMS power, power factor, fundamental frequency etc. When examining the EPM_Power VI I noticed that the real power is calculated by averaging the values of the instantaneous power of the waveform.This makes sense if you are averaging one period of a waveform at the time. However, how does this VI know when a period starts or stops? It apparently just averages all the incoming values. What if my frequency changes very rapidly very often. How accurate will this VI be then?

Regards,

[ThiCop]

Hello,

The "Power" VI provided in the EPM palette just averages over the size of the array provided at the input. If this doesn't fullfill your needs you can always adapt the provided VI to your needs.

This results in: 

small arrays => more accurate for high frequencies

big arrays  => more accurate for DC measurements

The interpretation of the vague terms big and small depends on at which rate your program calls the "power" VI.

[daniii]

I'm trying to make a VI that shows in which quadrant is the apparent power, the idea is to acquire the voltage and current data, but for now I'm just working with the program without connecting anything. I tried using the control "power" but I can not get the output. Although the SubVI "power" has the corresponding outputs that serve me (the power factor, reactive power etc.) they did not appear as output in the block diagram.

Tnks!

BTW I found no tutorials on this subject with examples ...help?

[ThiCop]

Hello,

I don't completely understand what you're trying to do.

Is it possible to upload a VI of what your currently trying to do?