When a voltage V causes a current I to flow through a reactive load Z, the complex power S is:
S = VI* where I* is the conjugate of the complex current I.
Z = R + jXL
I = IP – jIQ
cosf = R / |Z| (lagging)
I* = IP + jIQ
S = P + jQ
An inductive load is a sink of lagging VArs (a source of leading VArs).
Z = R – jXC
I = IP + jIQ
cosf = R / |Z| (leading)
I* = IP – jIQ
S = P – jQ
A capacitive load is a source of lagging VArs (a sink of leading VArs).
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