# Mixed Power Factor data on 3 phase service



## Southeast Power (Jan 18, 2009)

I recorded data from a service we are changing and I noticed that two of the three phases have PF in the .80s and .90s while the other leg is in the .50s and .60s. 
Have you guys had any experience with this? How can the PF be corrected on one phase.
Also, I 99.9 suspect the the low PF is on the hileg as its the smallest load. 
Its a small factory with 50 or more small motor loads and a 50hp and a 20hp screw compressor. No HVAC except for a dozen or so 1.5 hp fans hanging from jack chain.

This is a PDF of the data: 

https://www.dropbox.com/s/w5hjydz8d8o9ynr/AQIrguide 02 16 2019.pdf?dl=0


----------



## CoolWill (Jan 5, 2019)

The power factor on a 4 wire delta can be all kinds of wonky. I don't know what's going on in your building, but I do know that 50% PF is not uncommon in perfectly fine 4 wire deltas with lots of motors.


----------



## splatz (May 23, 2015)

Southeast Power said:


> I recorded data from a service we are changing and I noticed that two of the three phases have PF in the .80s and .90s while the other leg is in the .50s and .60s.
> Have you guys had any experience with this? How can the PF be corrected on one phase.
> Also, I 99.9 suspect the the low PF is on the hileg as its the smallest load.
> Its a small factory with 50 or more small motor loads and a 50hp and a 20hp screw compressor. No HVAC except for a dozen or so 1.5 hp fans hanging from jack chain.
> ...


Will the software give you that as an excel .xls or as a .csv text file?


----------



## nrp3 (Jan 24, 2009)

So, by changing to a 3ph wye on a new service, would that help? What does this have, mostly 1 ph motors with a few 3ph? I don't do a lot of 3 ph stuff so the whole power factor thing kind of boggles my small mind.


----------



## splatz (May 23, 2015)

nrp3 said:


> So, by changing to a 3ph wye on a new service, would that help? What does this have, mostly 1 ph motors with a few 3ph? I don't do a lot of 3 ph stuff so the whole power factor thing kind of boggles my small mind.


I am trying to understand it better but power factor is there with single phase as well as three phase. 

I think you'd always expect the higher power factor on the high leg. The idea is to have three phase available for motors (usually) and 120V available for lights receptacles, etc. 

So the three phase inductive loads are heavy on all three legs, but most of the resistive loads are on the not-high-legs. 

So when you draw the power triangle, the reactive power will be similar for all three legs, but the not-high-legs will have longer true power, which will flatten out the triangle / reduce the impedance phase angle / lower the power factor. 

If it's a place where the shop (motors) is big and the office (plugs and lights) is little, you'd see less of a difference in power factor on the high leg. If the non-three-phase loads are not much of the load, you'll get a bigger difference in power on the high leg.


----------



## nrp3 (Jan 24, 2009)

I've seen this explained a bunch of ways with leading and lagging. Motors push it one way, data center loads, ups's etc, push it in the other direction. I've just never really been able to grasp it or say that I truly understand it. I know from my end, sizing a generator may require a much larger generator than it would seem so it won't have trouble with voltage regulation. What interests me, and whether what he's looking at is really a problem or not, either financially (from the power company?) or just something he'd like to correct?


----------



## emtnut (Mar 1, 2015)

nrp3 said:


> I've seen this explained a bunch of ways with leading and lagging. Motors push it one way, data center loads, ups's etc, push it in the other direction. I've just never really been able to grasp it or say that I truly understand it. I know from my end, sizing a generator may require a much larger generator than it would seem so it won't have trouble with voltage regulation. What interests me, and whether what he's looking at is really a problem or not, either financially (from the power company?) or just something he'd like to correct?


For consumers, they only pay Kw, so there is no financial gain to correct it.

As far as power factor, the lower the number is, the more foam on the beer:biggrin:


----------



## nrp3 (Jan 24, 2009)

I've seen this too, and while I love beer, it still goes over my head.


----------



## splatz (May 23, 2015)

I think the foam is the current that's involved in building up electrical fields or charging capacitors, it is measurable current and so creates an appearance of power in the sense of current x voltage - but it's not actually consumed by the load, so it's not true power. 

I think the power company doesn't like it because they have to build a grid to supply the apparent power, but only get to charge you for the actual power.


----------



## nrp3 (Jan 24, 2009)

That's why I thought maybe the customer was seeing a penalty. I figured it was a measure of efficiency and kind of left it at that. That's been a reason why I haven't really thought about a PQ meter because I wouldn't know what the hell I was looking at. I'd like to get a good device to help me better watch loads and peak loads in KW not just KW/hr, but again not sure what I want. All I know is this stuff isn't cheap.


----------



## emtnut (Mar 1, 2015)

When you have an inductive load (or a capacitive load) , the voltage and current waveform is delayed.

Looking at the graph, if you multiply the voltage by the current at any given time, you get the Kw. But the poco still needs to supply the full current, as if the 2 waves were in sync ... the KVA

Does that help more ?


----------



## nrp3 (Jan 24, 2009)

I've seen this too and accept it for what it is. I think maybe because I haven't seen it in action I can't relate to what it means in the field. Or maybe I'm not too bright.

But I do appreciate you trying to help explain it. Interesting subject and if I discuss enough maybe it'll make more sense.


----------



## splatz (May 23, 2015)

emtnut said:


> When you have an inductive load (or a capacitive load) , the voltage and current waveform is delayed.
> 
> Looking at the graph, if you multiply the voltage by the current at any given time, you get the Kw. But the poco still needs to supply the full current, as if the 2 waves were in sync ... the KVA
> 
> Does that help more ?


I thought inductive loads lag and capacitive loads lead?


----------



## emtnut (Mar 1, 2015)

splatz said:


> I thought inductive loads lag and capacitive loads lead?


Yes. I know some guys here use the eli the iceman thing, but I always liked the 'you can't change the voltage instantaneously across a capacitor, and you can't change the current instantaneously across an inductor'.
Therefore the lag of current in an inductive circuit or the lag of voltage in a capacitive circuit.


----------



## Southeast Power (Jan 18, 2009)

splatz said:


> Will the software give you that as an excel .xls or as a .csv text file?


Yes. I just made it a PDF to upload it to Dropbox.
I can for use upload the .csv the recorder puts out.

https://www.dropbox.com/s/skfsvqzkm5c9k9r/AQIrguide 02 16 2019.csv?dl=0


----------



## micromind (Aug 11, 2007)

On a 240 ∆, I would expect the PF to be lower on the high leg since motors are about the only thing on it. 

A typical 1HP 3Ø motor that's loaded to half its capacity will have a PF of about 50%. At 75% load, it'll be about 60%.

As the HP goes up, the PF goes up as well. 

I wouldn't worry much though, a low PF on the high leg will have very little effect on anything unless the service is large enough to be billed for VARs.

If it needs to be brought up, an easy way to do so would be to move all 240 loads that do not involve the neutral to the high leg and one of the other phases. Especially resistive loads, like water heaters and the like.


----------



## Southeast Power (Jan 18, 2009)

Interesting comment about the partially loaded motors.
This plant works thin aluminum shapes. Most of the machine work is manually operated electric punches and shears. Dozens of work stations with vintage 2 hp motors.


----------



## nrp3 (Jan 24, 2009)

These have two transformers instead of three? The few that I've seen the second is smaller, would you need to be careful about how much load you moved over?


----------



## splatz (May 23, 2015)

Southeast Power said:


> Interesting comment about the partially loaded motors.
> This plant works thin aluminum shapes. Most of the machine work is manually operated electric punches and shears. Dozens of work stations with vintage 2 hp motors.


I have a customer with very old punch automatic punch presses and manual shears. The presses have a BIG flywheel, the clutch engages and the energy in the flywheel drops the hammer when they punch. I imagine the flywheel is so big that the surge in power after they punch is small. 

I think the shears have a similar mechanism but the manual shears idle much much more and of course don't have the monstrous flywheels. If that's how it works I could see how in a plant with a lot of manual machines there would be a lot of idling at low current / crappy power factor and a little high current / good power factor. 

If you could see a waves on a single machine, you'd probably see a lower current wave lagging the voltage quite a bit, with peaks after the clutch is engaged where the lag is much less. With a bunch of machines, since they don't all punch in unison, you probably couldn't see a thing on the service.


----------

