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Best Equipment for Power Factor Correction/Best Analyzer for the same

Best Equipment for Power Factor Correction/Best Analyzer for the same

Best Equipment for Power Factor Correction/Best Analyzer for the same

(OP)
I have seen the GE PFC equipment and am leaning towards it, but wondered also what equipment to use to analyze PFC in large industrial plants.

Any suggestions?

 

RE: Best Equipment for Power Factor Correction/Best Analyzer for the same

My first step in analyzing plant power factor is to see the accounts payable department and request copies of the utility power invoices for at least the previous year and for two or three years if available.
 

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Best Equipment for Power Factor Correction/Best Analyzer for the same

I'm a big fan of "on-load' PFC capacitors, meaning you have individual small caps at each contributing induction motor. Simple, effective, no chance of over correcting.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln  
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies  

RE: Best Equipment for Power Factor Correction/Best Analyzer for the same

I like to take your technique one step farther. I try to correct the largest motors to unity. That is often enough to bring the overall power factor above the penalty threshold.  

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Best Equipment for Power Factor Correction/Best Analyzer for the same

Both the above recommendations are right on. As for the equipment needed for determining PF, all you need is some form of metering that will either measure the PF directly or allow you to calculate form other values such as kW, V and amps etc. Theses may include a power quality meter or a combination of ammeter, volt meter and watt meter.

You also need to determine if correcting the PFC will result in some kind of tangible benefit such as savings in money and reduction in penalty.  You may find this of interest www.srengineersct.com/Newsletters/May%202009-News%20Letter-PFCC.pdf

Rafiq Bulsara
http://www.srengineersct.com

RE: Best Equipment for Power Factor Correction/Best Analyzer for the same

(OP)
I know how to find customers with low PFC and high penalties. I have customers that will benefit.. I just have to make sure that the PF does not drop down below ".9", after I adjust the PFC. Also.. I know that PFC sometimes causes high harmonic distortion. I do not want to cause problems in the factory if I correct the power factor and then they start losing power supplies due to high heat from high THD.

The answers here sound like there is a couple of machines in the factory at fault for bad PFC. I am talking about a manufacturing facility with over a hundred machines.

RE: Best Equipment for Power Factor Correction/Best Analyzer for the same

It applies to the type of manufacturing facility you describe as well. You can always place automatic PFCC system for a group of loads such as at MCCs or distribution boards or at the main switchboard.

GE, Eaton, Siemens, SQD and the like, all make such systems. Do a web search.

Or perhaps you can rephrase your question, if we misunderstood.

Rafiq Bulsara
http://www.srengineersct.com

RE: Best Equipment for Power Factor Correction/Best Analyzer for the same

(OP)
I appreciate your answers. Thank you.

I have a large industrial customer. They have many induction motors in manufacturing equipment, many VFD's and large AC units to boot. Do you recommend and individual assesment of each machine? Or do you recommend a automatic PFC system? Also, how do you assess/prevent harmonic problems that can be caused by PFC correction?

RE: Best Equipment for Power Factor Correction/Best Analyzer for the same

That is a project in itself. You need to hire a professional electrical engineer to do a study and make recommendations.

VFD should have no power factor issues, plus they do not like capacitors. Depending on the details and scale of the system, a system simulation on a software may be required to perform an harmonic analysis. The existing harmonic spectrum analsyis is needed first, which is relatively simple using a PQ analyzer.

In the original post you indicated you are already leaning toward GE PFC equipment..how did you reach that point without an analysis?

Rafiq Bulsara
http://www.srengineersct.com

RE: Best Equipment for Power Factor Correction/Best Analyzer for the same

All of the biggest disasters I have seen with VFD installations have been the result of automatic PFC bulk correction systems interacting with the VFDs. I prefer to stay clear of recommending them in plants with VFDs, I would now add those with HID lighting systems and any other SMPS based conversion equipment. Yes I know, that essentially means almost all industrial facilities now. In my opinion, the perceived savings from a bulk APFC system over on-load PFC caps, even if hundreds are involved, is immediately null and void the first time the APFC system reacts incorrectly to something and fries every VFD front end and SMPS in the plant, causing a long shut down for repair. And yes, I have seen that happen, twice. One, a fish processor in Alaska, saved $20,000 using an APFC system over on-load caps, but Murphy (of Murphy's Law) stepped in and software glitch caused a sudden over correction which fried 20+ VFD front-ends, shutting the plant down for a week in the peak processing time, costing them millions of dollars.

Waross' amendment to my suggestion makes the best sense; start off correcting the biggest offenders, then expand down from there until you have the situation under control. APFC systems try to do this digitally by adding and subtracting caps, but Murphy rules the world and any glitch affects the entire network. If you must consider a bulk PFC correction system, try picking your largest running continuous load and put a Synchronous motor on it to run as a synchronous condenser. I even know of a couple of facilities that have a large synchronous motor operating as a condenser with no load attached at all! That's because, as Rafiq suggested, they did an in depth evaluation of their penalty situation with the utility and discovered that even though it appeared to be a "waste", the economic benefit was enormous.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln  
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies  

RE: Best Equipment for Power Factor Correction/Best Analyzer for the same

To expand upon what others have said, you are going to have to characterize the load types AND the exact type of power factor problems you have.

Back in the old days, everyone assumed 'bad power factor' was an inductive load and could be corrected with a simple application of caps. No more. Power factor now includes the circulating harmonic currents that many non linear loads draw and must be corrected with different equipment.

Make sure that whoever does the study, they consider the harmonics problems in addition to inductive loads. And if your solution is in fact a capacitor bank, make sure that the plant down the road doesn't have a bunch of VFDs, or your caps will become a sink for their harmonic currents.

RE: Best Equipment for Power Factor Correction/Best Analyzer for the same

(OP)
Thank you all very much for the wealth of issues you have brought to my attention. My goal is to perform such analysis on large industrial factories and install robust and effective power factor correction. I wanted suggestions on the type of data acquisition equipment I can use for this type of analyses. BIM is a growing part of our field and improving a large energy users efficiency will benefit them and myself.

 

RE: Best Equipment for Power Factor Correction/Best Analyzer for the same

The harmonics problem is very real. If your transformer has more than about 10 % non-linear load - some say 15 % - then you can still use PFC capacitors, but you need to put reactors in series to steer away from any possible resonance with harmonics.

There is also a problem with automatic PFC control with switched capacitors if you have an ungrounded grid (IT grid). The switching sometimes causes transients that fry the VFDs. Be sure to make the switching in the zero crossings and you will not have that problem. But - you must make sure that you have a very reliable system. One false swiching can harm your VFDs.

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: Best Equipment for Power Factor Correction/Best Analyzer for the same

The low hanging fruit can be harvested with a few hours investment in time spread over several days.
1> Investigate the tariffs and the basis for PF penalties.
2> Request several years back power bills. (The instrumentation to measure the PF that is incurring penalties is already installed by the utility.
3> When you have the information, build a spread sheet and look at how many KVARHrs per month you need to get above the penalty threshold. Divide down to KVARHrs per Hour.
4> Look at which machines may be corrected to 100% and calculate how many KVARHrs per month you may gain from each machine.
This is the low hanging fruit. This method is not always applicable and may not serve as well for distortion PF issues, but it is quick and dependable and economical where it may be applied.
If the low hanging fruit will do the job, why do more?
I explain to the customers that there may occasionally be small penalty charges but it will probably be cheaper to pay the occasional charge than to avoid it.

Bill
--------------------
"Why not the best?"
Jimmy Carter

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