Comments on “apparent and reactive powers in three-phase systems: in search of a physical meaning and a better resolution”

It is shown in this comment that it is not so obvious that the apparent power S “has a clear physical meaning “ as it is asserted in the paper “Apparent and Reactive Powers in Three-Phase Systems: In Search of a Physical Meaning and a Better Resolution “ published by A. E. Emanuel in ETEP 3 (J993) no. I. Moreover, the author of the discussed paper misinterprets power properties of unbalanced systems. He asserts in Section 2 that, apart from the active power P, each power in systems with sinusoidal waveforms represents the amplitude of an oscillation of power. The apparent power S in unbalanced systems may be higher than the active power P, however, despite of the lack of any oscillation of instantaneous power, since the direction of energy flow may not change with the load unbalance. The unbalanced power of a resistive unbalanced load cannot occur as a consequence of power oscillation since such a load does not have any capability of energy storage.