Power Factor

[mobile_bob]

here is another interesting discussion that helps to muddy the waters,

http://cr4.globalspec.com/thread/13917/Diesel-Generators-And-Power-Factor

as you can see there are opinions and rationale on both sides of the issue, and this
seems to be typical of discussions on pf and its correction even on EE forums.

i personally ascribe to the theory presented in #4, which btw is pretty much what i posted earlier, but
it is just as clear from that discussion that there is opposing views.

so i guess, maybe the answer is
go ahead and power factor correct if you are able to do so economically, then test to see how the result
relate to improved fuel efficiency for your system?

maybe there are some cases where it makes a real difference, and others where it makes little or no difference?

bob g

[BruceM]

Thanks, Bob.  I won't be pitching PF correction anymore unless we find out otherwise.  The guys with ST-5's have nothing to worry about- they have plenty of extra capacity for low PF heating. 

[mobile_bob]

Bruce:

because of the importance of this topic and its repetitive nature in coming up from time to time
and wanting to get it right on our forum, i contacted Bill Rogers and had him come take a look
at this thread and asked for his input.

the following is from Bill Rogers:
quote

"1. The extra amps generate extra real losses within the generator and wiring system (I-Squared-R)

2. The extra amps cause additional voltage drop within the generator and wiring system. A motor load will respond to the lower voltage by drawing extra current to make up for it (which further increases the I-Squared-R losses.) Generators with an AVR will ramp up the excitation power to overcome a portion of the extra drop. Either way, more fuel is consumed.

One other thing, Bob. Reactive amps cause MORE voltage drop within the generator than active amps. Generators rated at unity power factor really struggle to maintain good output voltage against a poor PF load. PF correction pays off best with generators rated at PF=1.

I think you guys are under-estimating the fuel savings of going from say a 70% pf to 95%, but that's easy to resolve - just run a couple of tests... Grams/KWH @ 70% vs Grams/KWH @ 95%. No need to guess at it!"

end quote

it appears like we need to actually do some consumption testing to determine for sure what  effect improving power factor has on fuel consumption
and perhaps quantifying it as well.

this may show a small improvement in some applications, and a much larger improvement in others?

to whatever extent there is an improvement it seems prudent to determine what it might be, doesn't it?

bob g

[BruceM]

Sounds like some real PF vs fuel consumption data is needed.  Alas, it can't be me, I'm still a wreck, health-wise.

[mobile_bob]

Bruce:

i agree wholeheartedly

we need to get small research group together, tooled or instrumented up enough
to get some meaningful results, work on a set of basic and accepted test procedures
and to the deed.

we are never going to know for sure until we do some testing, and i am up for doing a part in it.

i just don't think my numbers are going to be very meaningful without at least a couple others doing
the same type of testing independently of each other.

i would be all over finding out under what conditions power factor correction improves fuel consumption numbers
and under what conditions where it might not improve enough to justify the expense.

just not sure if my s195 changfa coupled to a st7.5 is going to return the same results that a more typical
6/1 driving a st5, but i could be wrong!

wouldn't be the first, likely won't be the last



bob g

[WGB]

I never thought this thread would have this impact!
I'm humbled that Bill Rogers commented, thanks Bob.
Anyway, I didn't care about fuel usage, I just want to work toward a fine tuned system.
Lowering amp draw, or lowering heat in equipment or conductors was my goal.
Like his book explained if you get your PF in line you'll be able to start and run more load.
Then it would be a given fuel will be saved?
I'm all for doing testing, but my main target is getting up and running at this point.

[mobile_bob]

WGB:

sorry if i stole your thread and took it in a direction you weren't interested in, sometimes i get a bit
wound up about a specific topic, and powerfactor is just such a topic.

btw, i think as far as fine tuning a system, why not?  seems like a prudent thing to do in my opinion

for whatever that is worth? 

bob g