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Chapter 2 Measurement Procedure
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Sample Measurements
I U 1φ PMeterλ 1φ PF Meter λ
1.000 1.000
*
0.847 0.750
* Distorted waveforms with crest factor of 1.9.
[Difference in λ between 1φ P Meter and 1φ PF Meter]
For distorted waveforms, the value of power factor λ
may differ between the 1φ P meter and 1φ PF meter.
The difference is due to the fact that the 1φ P
meter calculates λ from active power and apparent
power, while the 1φ PF meter assumes a sine wave
and calculates λ from the phase angles of the
voltage waveform and current waveform of that sine
wave. Therefore, phase-angle measurement serves
as the basis for the 1φ PF meter. Distorted
waveforms and those with noise superimposed may
prevent the meter from measuring power factors
accurately or even at all. Therefore, use λ of the 1φ
P meter for distorted waveforms.
Power factor λ of the 3φ PF meter is also obtained
from the phase angles of voltage waveform and
current waveform of an assumed sine wave.
Therefore, accurate measurements may also not be
conducted with distorted waveforms or those with
noise superimposed. The following example shows
the measurement of power factor λ from power
values on a three-phase circuit.
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