The role of Poynting's vector in polyphase power calculations

This paper is a tutorial contribution to the clarification of the role played by Poynting's vector (PV) in power calculations. In polyphase power systems, the standard computation of the instantaneous power is usually performed by using a summation of voltage–current products. We show analytically how such a result can be deduced directly from Maxwell's equations together with the evaluation of the PV flux. A simple application example is provided to illustrate the issue under discussion. Copyright © 2008 John Wiley & Sons, Ltd.