| , ?the minimum PF is not zero when no power is
|> being developed.
| And how is power developed? If you mean dissipated then please tell me
| what is the PF of a theoreticaly perfect (lossless) reactance of
| either type?
I'll try some explanation here.
If by lossless you mean that all power being supplied goes into delivering
motive power to the rotating device, then this does not change the PF at all.
It can still be no more than 1.0. You just don't have any resistive losses
that would reduce efficiency (a different measurement).
If you are referring to a plain reactive device, an inductor or capacitor,
with no resistive loss involved anywhere, then PF is zero and no power is
lost anywhere. Of course, this is never a reality.
Power can produce work done by a motor, as well as heat. If you include the
heat in the equation, you would have a slightly higher PF than if you omitted
the heat. But it can still never be above unity.
Basically, unity PF means you are using all the power taken from the source.
Less than unity means you are giving some back in terms of current/voltage
phase angle difference. You can have a negative PF, which would mean more
power given to the source than taken from it. That's what you would get with
a generator feeding the system.
At zero PF, the phase angle of the current is at 90 degrees from the voltage.
During half of each half-cycle, power is taken from the source, and during
the other half of each half-cycle, power is given back in the same amount.
The phase angle tells you the PF when everything is a perfect sine wave.
The calculation is more complex when harmonics are involved.
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