Measurements
9410 series
Measurements
Power and power factor
The sampled measurements taken at the meter’s voltage and current inputs provide
data for calculating power and power factor.
In a balanced 3-phase alternating current (AC) power system source, the AC voltage
waveforms on the current-carrying conductors are equal but offset by one-third of a
period (a phase angle shift of 120 degrees between the three voltage waveforms).
Power factor (PF)
Power factor (PF) is the ratio of real power (P) to apparent power (S).
Power factor is provided as a number between -1 and 1 or as a percentage from
-100% to 100%, where the sign is determined by the convention.
P F
P
S
---
=
An ideal, purely resistive load has no reactive components, so its power factor is one
(PF = 1, or unity power factor). Inductive or capacitive loads introduce a reactive power
(Q) component to the circuit which causes the PF to become closer to zero.
True PF and displacement PF
The meter supports true power factor and displacement power factor values:
•
True power factor includes harmonic content.
•
Displacement power factor only considers the fundamental frequency.
NOTE:
Unless specified, the power factor displayed by the meter is true power factor.
Apparent, active and reactive power (PQS)
Apparent power (S) is the capacity of your measured power system to provide active
(real power, P) and reactive power (Q).
A typical AC electrical system load has both resistive and reactive (inductive or
capacitive) components. Resistive loads consume real power (P). Reactive power (Q)
is either consumed (inductive loads) or generated (capacitive loads).
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