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- Thread starter mrhingle
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gneill

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You've remembered correctly regarding how to determine if a source is delivering (sourcing) or consuming (sinking) power.

You can use superposition if you wish. But it looks like you've already determined the net current. What is the the assumed direction direction of your current? Do you know how to determine the complex power associated with a voltage source given the current out of the + terminal (same as into the - terminal)? The real component of the complex power is the real power.

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Complex power = 1/2 VI*. Never considered direction of current when looking at it. Pretty new concept to me. So how do I use the assumed direction of current to know if the voltage source is absorbing or delivering?

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gneill

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Without loss of generality, make V1 angle = pi/6, then V2 angle = 0. V1 on left, V2 on right.

Compute complex I. Using superposition is a good idea.

Compute I*, the complex conjugate of I. Also compute complex conj. of V1. You already have complex conj. of V2 of course.

Then compute P1 = 1/2 (V1 I* + V1* I) and P2 = 1/2 (V2 I* + V2* I).

Either source will be generating real power if its P is +, and will be absorbing real power if its P is -.

Hints:

1. Use exponential notation thruout, including Z.

2. [exp(j theta)]* = exp(-j theta).

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