Yes there are real electrical engineers lurking on this group. Paul H is
one, Daestrom is another, Ben Miller is one. I also am one. There are others
and some definitely are not engineers- wecandoit, and the guys who spend
their time in infantile insults are not.
Do we deal with digital transmission
lines? - I don't and some of the others don't- power transmission and
utilization is far more fun.
You got a good answer to your question from Paul and Martindale pointed out
some facts. In considering residential service, the charges are based on
energy as read by a KWH meter which actually measures the real power* time.
Your KWH meter, at .38KWH over 1.62 hours indicates an average real power of
380/1.62 #0 Watts (rounded to 2 significant figures). This meter doesn't
give a hoot about power factor Your killawatt indicates 205 Watts - The KWH
meter is actually more accurate by a fairly large margin (money is
In determining your costs- consider only the real power as that is all that
the KWH meter cares about.
The power factor as found from watts/Volt amps 5/269 =0.76 as opposed to
the measured 0.78 . Your voltage times current indicates 259VA not 269VA so
there are a few discrepancies but this is to be expected. The measured
Volt-amps includes the effect of reactive volt amps which is a measure of
energy put in during part of the cycle and returned in another part of the
same cycle =average of 0 (in every 1/60 second) so it doesn't register in
the watt reading. This is what gives the power factor which is the ratio
between true power (watts) and the apparent power or volt-amperes. Using
your measurements the reactive Volt amps 4VAR The power factor of
different loads will depend on the load. A light bulb or heater will be
unity power factor as they are pure resistance loads. A single phase motor
will have a power factor at full load of the order of 0.7 or so at full load
and about 0.5 at no load because it is inductive. Fluorescent lamps have
inductive ballasts so they will also have a power factor less than unity.
All this tells us nothing about the efficiency of the generator, the
transmission line or even the appliance itself. At this power level trying
to correct power factor (at the appliance- not at the house service
entrance) might save a couple of watts (line losses as Paul had indicated)
but would cost more than it saved so why bother.
Does this help?
Don Kelly email@example.com
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