Hello!
I want ur help for calculation of power Factor to desplay on PowerPanel HMI. I have tranducer inputs from CT's and PT, 4-20mA all. PLC is SLC.
Waiting reply...
GILL

check this out

http://www.allaboutcircuits.com/vol_2/chpt_11/3.html

Power Factor - Found this little gem... could't resist fellas..

To understand power factor, we will first start with the definition of some basic terms:
KW is Working Power (also called Actual Power or Active Power or Real Power). It is the power that actually powers the equipment and performs useful work.
KVAR is Reactive Power.
It is the power that magnetic equipment (transformer, motor and relay) needs to produce the magnetizing flux.

KVA is Apparent Power.
It is the "vectorial summation" of KVAR and KW.
Let's look at a simple analogy in order to better understand these terms....

Let's say you are at the ballpark and it is a really hot day. You order up a mug of your favorite brewsky. The thirst-quenching portion of your beer is represented by KW (Figure 1).
Unfortunately, life isn't perfect. Along with your ale comes a little bit of foam. (And let's face it...that foam just doesn't quench your thirst.) This foam is represented by KVAR.
The total contents of your mug, KVA, is this summation of KW (the beer) and KVAR (the foam).

The Beer Analogy





Figure 1


So, now that we understand some basic terms, we are ready to learn about power factor:

Power Factor (P.F.) is the ratio of Working Power to Apparent Power.
P.F. = KW / KVA
Looking at our beer mug analogy above, power factor would be the ratio of beer (KW) to beer plus foam or (KVA).
P.F. = KW
KW + KVAR
. = Beer
Beer + Foam

Thus, for a given KVA:
• The more foam you have (the higher the percentage of KVAR), the lower your ratio of KW (beer) to KVA (beer plus foam). Thus, the lower your power factor.
• The less foam you have (the lower the percentage of. KVAR), the higher your ratio of KW (beer) to KVA (beer plus foam). In fact, as your foam (or KVAR) approaches zero, your power factor approaches 1.0.
Our beer mug analogy is a bit simplistic. In reality, when we calculate KVA, we must determine the "vectorial summation" of KVAR and KW. Therefore, we must go one step further and look at the angle between these vectors.

Thats why we like 90%-95% power factor....

good explanation

I guess when you live on the "other side" everything eventually works its way around to alcohol. LOL Good one Sleepy !!

Looking back at the original questions...I have tranducer inputs from CT's and PT, 4-20mA all.
Since the AC signals are converted to DC(4-20ma), how can you calculate the power factor if you don't know the phase angle between the two?
I feel he should wire in a power factor meter and bring the signal in from that unit.

Ok. Can anyone tell me the formula for real power calculation and kvar calculation. Aictual problen is this.
The bear example is excelent to understand the basic. Thanks.
Waiting Reply...
GILL

On a balanced 3 phase star or delta connected load
P=1.732051 x VL x IL x PF
P= total power
VL= line voltage
IL =line current
PF=power factor
So if you think you have a balanced system and your voltage is stable you might get an approximation using this. I know in the real world nobody would do this but what the hell it sort of answers the question
Phil
1.732051
1.732051
1.732051

Great example Sleepy! Thanks

But you still can't get the power factor without knowing the power.
There is no way to get power factor with just CT & PT transducer (4-20ma) inputs.

mmm .. so wouldn't that make you think how a power meter would work then ?

If you use basic power monitor 1000 it will give more parameters with ethernet connectivity


http://forums.mrplc.com/index.php?showtopic=9715&hl=

I agree but was not trying to answer how I would go about it just answering the question in the simplest form I could find so that he might realise he was barking up the wrong tree. Hopefully knowing the variables you need to monitor should point him in the right direction