Active Power

[Salvio]

Hi.
I'm trying to calculate the value of the Active Power of my two signals. I'm looking at IEEE 1459 and it says that:

P=(1/kT)*∫p*dt

where:

1- p is the instantaneus power

p = vi ,  where  v = 2V sin(ωt) and i = 2I sin(ωt – θ)  with V and I in RMS values;

2- T= 1/f is the cycle (s),
k is an integer number,
τ is the moment when the measurement starts.

Now before to do that i've done an FFT of my signals on 10 periods. So i'm working in frequency domain.
How can i calculate this value? can u show me a VI?
Because in the VI that i've done i've tried to do a summary of the v*i but it doesn't work...plz can u help me?
Tnx a lot.

[Salvio]

this is the VI that i'm trying to do...plz help me

[Chuck_81]

Have you already tried using "Integration and differentiation" function located under "Mathematics" subpalette on the block diagram? Two of them maybe could help you for the integration:

1. Numeric Integration.vi: Performs numeric integration on the Input Array using one of four popular numeric integration methods. The data type you wire to the Input Array input determines the polymorphic instance to use;
2. Integral x(t): Performs the discrete integration of the sampled signal X. Integral x(t) calculates a definite integral. The value of the output array at any value x is the area under the curve of the input array between 0 and x;

These functions are included into the "Integration and differentiation analysis tools"; if you don't have this package installed you can use the "Integral.vi" Express VI, as suggested into the following example inserted into the Example finder:

NI Example finder -> type integration; the example is "Integral.vi"

Hope this helps.

Best regards,

Fabio