# LabVIEW

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## Reactive power

Hello Every one.

I need to calculate reactive power by phase shift method.I am using two sine waves for which I have to delay one sine wave by quarter of a cycle.Can any one guide me how can I produce this delay?

Thanks

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## Re: Reactive power

When you say "I have two sine waves", do you mean "there are two signals in the real world that are sinusoids of some frequency and amplitude and I need to sample them (at some unspecified frequency) and do some computations (not clearly defined) ...", or do you mean "I have sampled data from two sinusoids and ..."?

Why not use Matlab?  Why are you asking a question in the LabVIEW Forums without saying anything about LabVIEW (like Version number, or whether 32 or 64-bit), or your experience (never used, just beginning, 5 years experience, etc.)?

Bob Schor

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## Re: Reactive power

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=== Engineer Ambiguously ===
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## Re: Reactive power

As you can probably tell from the answers, your question is ambiguous.

It is trivial to generate a (complex) quadrature signal for a given frequency, then use it to determine the phase  of a signal that has the same frequency, but unknown phase.

Long ago I posted an example. (Sorry posting by phone. Don't have the link)

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## Re: Reactive power

I am beginer in labview.I need to calculate reactive power by time delay method(image is attached below).I am using Labview 2019.I am generating two signals (sine waves) by using basic function generator and I need to calculate rerative power.I set Voltages magnitude to 230 v and current amplitude to 1.5 A.You can understand by seeing the figure below.Thanks

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## Re: Reactive power

@Rehm wrote:

I am beginer in labview.I need to calculate reactive power by time delay method(image is attached below).I am using Labview 2019.I am generating two signals (sine waves) by using basic function generator and I need to calculate rerative power.I set Voltages magnitude to 230 v and current amplitude to 1.5 A.You can understand by seeing the figure below.Thanks

And people answered you in their previous posts (and you provided the answer, yourself!).  If you are using LabVIEW VIs as the "basic function generator", one of the first responses showed "add a phase difference of 90 degrees to one signal" (which, in your figure, is shown by "N samples = 90 degrees").  If, on the other hand, you have sampled signals, and if you know the sampling frequency and the frequency of the AC signal, then delay one by a quarter of a cycle and do the multiplication.

Bob Schor

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## Re: Reactive power

First of all, LabVIEW is a programming language, not a circuit simulator. We are dealing with numbers, not Volts and Amps.

You have three inputs, not two!

• u(t) from an ADC or simulated
• i(t) from an ADC or simulated.
• sampling frequency

Are these continuously acquired/generated and received one point at a time?

You have one output (reactive power). Is that just a scalar indicator? Should it be averaged over one cycle?

Assuming everything is in place, you seem to be mostly interested at the square box in the picture. Once you know the number of samples required for a 90 degree delay, you just need to program it. Right? You also need to decide what to do before the delayed signal is valid.

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