where S is apparent power, P is real power and Q is reactive power.

In this formula, I have two questions. Firstly, S, P, Q here are what

kind of power, average power? rms power (rms U

*** rms I)? Instantaneous**

power (U *I from moment to moment)? After clarify the definition, can

power (U *

anyone show a prove?

The second question is that I think, for energy, apparent energy should

be a sum of real energy and reactive energy. I learned this from

Andrew's article:

between apparent/active/reactive is different with power?

Finally, for these AC concepts, is there a good text book in amazon.com?

Thanks in advance.