MISINTERPRETATIONS OF SOME POWER PROPERTIES OF ELECTRIC-CIRCUITS

It might be expected that the meaning of the apparent power S, a quant ity of innumerable everyday applications for almost a century, is well understood. It occurs, however, that this meaning is still a matter o f discussions and some interpretations hard to accept are published. A lso it is suggested in some papers published recently that only oscill ations of the instantaneous power may cause an increase of the apparen t power S, which is not true. Misinterpretations that refer to fundame ntal notions such as powers could be particularly harmful for electric al engineering and should be eliminated as much as possible. Therefore , this paper shows that the apparent power does not have the physical meaning suggested recently. Also it shows that loads unbalance in thre e-phase systems does not cause any oscillation of the instantaneous po wer. The conclusion that loads unbalance causes oscillations of the in stantaneous power is a consequence of a substantial misinterpretation of this quantity in three-phase systems.