True power factor (PF) and displacement power factor (DPF) are commonly available on power
analyzers and loggers. At first glance (and in some situations), they appear to measure the same thing, but there is an important difference.
A review of their definitions, and when to use each is presented here. PF and DPF are both measures of the “efficiency” of power delivery, in the sense that they are ratios of the useful energy delivered to a load vs. the “effort” or “burden” on the electrical system by that load.
PF, or “true power factor” has the most straightforward definition, but DPF is perhaps more familiar in terms of the traditional power triangle relating Watts, VARs (Volt-Amps-Reactive),
and VA (Volt-Amps).
The displacement power factor (DPF), is the “power factor” of just the 60Hz portion of the waveform for voltage and current. Harmonic effects are inherently excluded from the calculation, and have no direct effect on the result...
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