Amprobe DMII-PRO Data-Logger-Recorder - Manual (Page 29)

Page 29
True Power Factor PF: The ratio of working power or Real Power, P, to Apparent Power, S. It meas-
ures how effectively electrical power is being used by the system. The Displacement Power Factor has
traditionally been calculated by examining the phase angle between the fundamental voltage and current
and is equal to cos (
θ).
This traditional method only works for linear, sinusoidal systems. The DM-II™,
however, calculates the True Power Factor, which also works for non-linear, non-sinusoidal systems.
Power factor can be leading or lagging, depending on the sign of the reactive Volt-Amperes Q (VAR).
The following table summarizes:
Power Factor Sign of Q Type of Load Current/Voltage Relationship
Lagging Positive Inductive Current Lags Voltage
Leading Negative Capacitive Current Leads Voltage
DM-II™ Total Power Quantities (P, Q, S, PF) for 3Ø Systems
3Ø 3W Delta and 3Ø 4W Wye configurations include total calculations for P, Q, S, and PF, based upon
the following formulas.
Total Power, P Total :
P Total =
P
ØA
+ P
ØB
+ P
ØC
Total Reactive Volt-Amperes, Q
Total
:
Q Total =
Q
ØA
+ Q
ØB
+ Q
ØC
Total Apparent Volt-Amperes, S Total :
Total Power Factor, PF Total :
PF =
P
S
PF
Total
=
P
Total
S
Total
S Total
=
√
P
2 +
Q
2
Total Total