ON THE DEFINITION OF POWER-FACTOR AND APPARENT POWER IN UNBALANCED POLYPHASE CIRCUITS WITH SINUSOIDAL VOLTAGE AND CURRENTS

This paper advocates much needed definitions for the apparent power S and for the power factor PF, in unbalanced polyphase circuits with sinusoidal waveforms. It is proved that the definition S' = (V(a)2 + V(b)2 + V(c)2)(I(a)2 + I(b)2 + I(c)2) has a definite physical meaning, lending itself to a convenient resolution in positive, negative and zero sequence, nonactive and active powers. It is suggested to represent the power factor with the help of the ratio P+/S, where P+ is the positive sequence active power.