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rattus

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If one had a series of v(t)i(t) product values, as many as needed, but no additional information, how would one go about separating the real and reactive powers from the instantaneous apparent power?
 
Hameedulla-Ekhlas

Hameedulla-Ekhlas

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rattus said:
If one had a series of v(t)i(t) product values, as many as needed, but no additional information, how would one go about separating the real and reactive powers from the instantaneous apparent power?
Click to expand...

apparent power is magnitude of complex power and how it could be instantaneous.
 
Smart $

Smart $

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rattus said:
If one had a series of v(t)i(t) product values, as many as needed, but no additional information, how would one go about separating the real and reactive powers from the instantaneous apparent power?
Click to expand...
Are we to assume sinusoidal AC? ...and linear load?
 
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Smart $

Smart $

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rattus said:
As many as you need, say a googol.
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Got Excel? Why not generate some numbers for us... but please not a googol. What would make it interesting is the product values not indicating the exact peaks or zero crossings.

Additionally, given only the procut values, there will likely be at least two answers. For example, |v||i| = |v'||i'|, where |v'| = |i| and |i'| = |v|.
 
Smart $

Smart $

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Smart $ said:
...

Additionally, given only the procut values, there will likely be at least two answers. For example, |v||i| = |v'||i'|, where |v'| = |i| and |i'| = |v|.
Click to expand...
"procut" is a typo for "product".

Thinking a bit more on this, you didn't ask for the values of v and i. ;)
 
Smart $

Smart $

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rattus said:
Instantaneous power cannot be complex because the addition is algebraic not phasorial. There is no power triangle as in the steady state.
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It's still "complex" in the literal sense, being made up of two parts. It could be complex numerically if one chooses to describe the waveform as a sine function of time... nothing different than what we do with voltage and current.

Anyway, futher thought on the matter leads me back to saying there are two answers because we cannot discern leading or lagging current by vi product information alone.
 
Smart $

Smart $

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LarryFine said:
Okay, show me the pic of a complete cycle.
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Perhaps this one...? (Nice and big so you can copy and draw on :cool:)

PFVAW10.gif
 
steve66

steve66

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I'll bite, or at least take a guess.

Power traveling to the load will have a positive sign (positive voltage and positive current, or negative voltage and negative current.)

Power traveling back to the source will have a negative sign (current and voltage are opposite signs).

So the real power would be the difference between the two.

From Smart's graph, the real power would be the difference between the area above the axis and the area below the axis.

Do I win a cigar??

Steve
 
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rattus

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Smart $ said:
It's still "complex" in the literal sense, being made up of two parts. It could be complex numerically if one chooses to describe the waveform as a sine function of time... nothing different than what we do with voltage and current.

Anyway, futher thought on the matter leads me back to saying there are two answers because we cannot discern leading or lagging current by vi product information alone.
Click to expand...

To avoid confusion, don't call it "complex". There are no complex numbers in p(t).

And, we are describing the vi product as sinusoids and an offset, but still no imaginary values. We would have to use rotating phasors to do that and we don't want to get into that quagmire just now.
 
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