Power Factor

[Rzn]

Dear All,

 

I am new one in this forum. This my very first question. Sorry for poor English.

I am working on a project where the following load will be connected at 400VAC 50HZ sustem:

 

(1) Asynchronous motors 800KW (300 motors)

(2) Asynchronous motors controlled by VFDs 300KW (7 motors)

(3) DC motors controlled by DC drives 600KW

(4) Single Phase Air Conditioning units 1.7KW x 15

(5) Light fixtures (Ballast type) 25KW/phase

 

Now I want to know what will be the resultant power factor of this type of combined load? as there is no way to measure the resultant power factor. What should be the capacity of PFI plant?

Any help will be highly appriciated.

 

 

[Rzn]

Dear Marke, mariomaggi and jOmega,

 

You are the most active members found in this forum but here is quite from you why? Is my question wrong? Please inform me as I have confused that no one is replying.

 

 

[marke]

Hello Rzn

 

The problem is that, apart from being very busy, we are not brave enough to take a guess on that.

 

The only way to find out is to make a measurement.

Please note however, that you have two issues here. You will have a displacemtn power factor due to the inductive motors, and distortion power factor due to the DC drives.

You can correct the inductive power factor with capacitors, but you can only improve the distortion power factor with the use of filters. - The distortion power factor would probably cause issues with additional harmonic currents through the power factor correction capacitors, so they may need to be detuned.

see http://www.LMPhotonics.com/pwrfact.htm

 

Best regards,

[Rzn]

Dear All,

I am wondering that in this very good forum in which the experts in power factor correction like Marke, Mariomaggi, Jraef and JOmega reply against question, why my question has been taking a time for replying?

I think that in designing a new plant, the same problem faces by engineers that they don't know about correct power factor of load but they have to design the PFC panels along with main LT power distribution panels. Then how they design the PFC panel? Is there not a rule of thumb?

The very first question which I have asked in this forum, is as following:

 

"I am working on a project where the following load will be connected at 400VAC 50HZ system:

 

(1) Asynchronous motors 800KW (300 motors)

(2) Asynchronous motors controlled by VFDs 300KW (7 motors)

(3) DC motors controlled by DC drives 600KW

(4) Single Phase Air Conditioning units 1.7KW x 15

(5) Light fixtures (Ballast type) 25KW/phase

 

Now I want to know what will be the resultant power factor of this type of combined load? As there is no way to measure the resultant power factor. What should be the capacity of PFI plant?

Any help will be highly appreciated."

[marke]

Hello Rzn

1. You have asked this question before and I have given you a reply. Please do not "Spam" the forum by repeating the questions, you will find that levels of support will reduce. - I have merged this topic with your previous topic to prevent clutter.
2. The advise given on this forum is by volunteers who have the right not to answer if they do not feel that they can add value, or if they are too busy etc. If you need a higher level of support, there are consultants who will help for a fee.
3. As previously posted, there is no single answer to this. The only way to find out is to make a measurement unless you can provide the absolute data on each motor and load connected. If you did this, you would probably not get an answer due to the time required to do all the calculations. We have to do this for a living and if we spend too much time answering questions on the forum, our income is reduced.

Best regards,

[mariomaggi]

Dear Rzn,

I wish to give my thanks to marke for his answer. I agree with him.

 

This is not a "paid call center" where you have the right to get an immediate answer!

 

To give a professional reply to your question, it is necessary to know many other operating details. For example: a VSD drive operating at very low speed and power should be considered as a capacitive load, the same at high speed will be more compensated. But with VSD you have firstly to consider harmonics!

Probably the best solution will be to install some harmonic filters and and automatic PFC correction unit.

Where are you located? The local energy cost and local standards could push to one solution or to another one.

 

... I've to start to work .....

 

Regards

Mario

 

 

[jOmega]

Dear Rzn,

 

The answer to your question is:

 

 

THERE CAN BE NO ANSWER

 

Any rules of thumb you might find, would not be worth the paper they are printed on.

 

If you are asking because you think you will need some value of power factor correction and/or harmonic mitigation, .....find a competent Power Quality engineer or consultant to do a system analysis and follow their recommendations.

 

That's the best advice we can give you.

[Bill Wynne]

Rzn,

I certainly don't have an answer for you on your dilema but I did want to encourage you to look at a device that is up and coming and very interesting to the field of electricity and the power factor.

Here is a website to look it over www.xpowertechnology.com

 

Sincerely

Bill Wynne

 

[marke]

Hello Bill

 

Welcome to the forum.

 

While the theory and examples of this technology may look convincing to some, I for one see this as power factor correction on a domestic supply and if this is what it is, then you will not reduce the KWHrs used and therefore not reduce the domestic power bill.

 

Power factor correction has been around for a long time and it has been proposed as a means of energy saving on many occasions.

The bottom line is that power factor correction will reduce the line losses, but not the KW consumed by the load.

If the supply meter is based on current rather than KWHrs, then you will possibly see a reduction. If the meter is based on KWHr (which is the norm) then you will not see a reduction.

 

Additionally, the domestic power factor is generally pretty high which is why the supply authorities do not monitor and charge for PF or KVA usage.

 

Please note, this forum is for non commercial usage. Product promotion is not allowed.

 

Best regards,

[jOmega]

That which follows is for informational purposes only and is neither an endorsement or promotion of the product and/or company discussed.

 

Hi MarkE......

 

Did you perchance .... see their videoes ?

 

I've posted them as an attachment hereto

(well, I thought I'd posted them; apparently the .wmv file sizes exceed attachment constraint)

 

So, click links to download video files :

 

Xpower Demonstration

 

Xpower saves in the Breaker Box

 

(note: 2nd download file appears to be missing its audio track)

 

Device is selling for $199.99 USD Retail.

Caveat Emptor!

 

[kens]

Hi jOmega, I missed the Video so thanks for the link. Interesting stuff. I thought there were laws about claims made on products?

Ken

[jOmega]

Hi Ken,

 

"Ladies and gentlemen. Pay close attention. Notice, at no time, do my fingers leave my hands!"

 

 

jΩ

[kezetrum]

Rizwan..

 

to decide what is the power factor..need more parameter should be taken..

 

you can apply some software, draw the single line diagram, put the input parameters, and based on your option conditions you can run it to get the power factor result from calculation..etap or edsa sometimes could help on designing..

 

Marke..

saying something like those softwares not for 'promoting product'..but if wrong to put please notify me

 

some case I use the software to help me on "electrical calculation" besides on my hand..

 

In my place..many guys also from NZ and Aus..BECA..as well from Canada..

 

thanks

 

new member

 

 

[jraef]

Hi jOmega, I missed the Video so thanks for the link. Interesting stuff. I thought there were laws about claims made on products?

Ken

 

It's all in the wording. If you pay attention, they never say it WILL save 25% on your electricity bill, it says it CAN save UP TO 25% on your electricity bill. This can be interpreted, from a legal standpoint, as anything FROM 0.000000001% up to 25%. So the tiny tiny little bit of watts loss savings in the conductors would validate that ambiguous claim from a purely legal standpoint. They also count on the fact that nobody is going to hire a lawyer over phony claims on a $200 product, and they are such a small potatoes company that a class action lawsuit would not net enough money to attract a hungry lawyer on their own. This is the reason why you never see big companies such as GE or Siemens trying to sell crap like this, they have deep enough pockets that some lawyer somewhere would love to take them on "on behalf of the consuming public", after collecting their fees off the top of the class action settlement of course.

[kens]

I also missed this at the bottom of the page

 

"This web site is posted by an Independent Business Owner of Forum Technologies, Inc.

The opinions listed in this site reflect those of the owner of this site, and do not reflect the opinions of the Company.

Please refer to Forum’s company site at www.myfti.biz to view the company’s product claims, representations, and warranties."

 

Ken

 

[jraef]

Here's a real laugher!

 

Look at their "Independent Test Results" page.

http://www.myfti.biz/FTI2006/images/Indepe...est_Results.pdf

 

The testing company, PTI, is in fact a legitimate professional testing service, so they had a reputation to uphold. This leads to the fact that they were apparently unwilling to flat out lie, although they may have conspired to "spin" the story their customer asked them to tell. Still, the true facts are in the report when you read it, just not explained properly!

 

They did 5 tests, or "experiments" using AC 1 phase motor loads. On 1 test, the WATTS remained exactly the same, even though the current went down! Gee, just what we have been saying. But it gets worse (for them). On 3 of the tests, the WATTS actually went UP with their device connected! That's right, UP!!!! Now we all know that the meter in our house is only measuring one thing; kilo-WATT-hours, watts times time. That's IT! These test reports show that on 4 out of 5 tests, there was NO savings in watts, in fact there was actually a loss on 3/5 of them.

 

On one test, the watts went down very very slightly, 7 watts out of 449, or about 1-1/2%, a far cry from their "25% savings" claim to be sure. On another page at the main website they show a payback calculator. The lowest savings they show on there is 5%, for which the payback is 7 years. Extrapolated for only 1-1/2% savings (assuming that is not just a testing anomaly), that makes the absolute best payback period available for their product to be over 23 years!

 

Absolutely ludicrous, and they publish it boldly, hoping beyond hope that the people who read it have no idea what it says!

[electrician3]

It's all in the wording. If you pay attention, they never say it WILL save 25% on your electricity bill, it says it CAN save UP TO 25% on your electricity bill. This can be interpreted, from a legal standpoint, as anything FROM 0.000000001% up to 25%. So the tiny tiny little bit of watts loss savings in the conductors would validate that ambiguous claim from a purely legal standpoint. They also count on the fact that nobody is going to hire a lawyer over phony claims on a $200 product, and they are such a small potatoes company that a class action lawsuit would not net enough money to attract a hungry lawyer on their own. This is the reason why you never see big companies such as GE or Siemens trying to sell crap like this, they have deep enough pockets that some lawyer somewhere would love to take them on "on behalf of the consuming public", after collecting their fees off the top of the class action settlement of course.

All I can add is my personal experience. And FACT !

My brother has an all electric house. Approached me to see if a power factor correction capacitor unit would help him lower his electrical bill. We bought one for $300 & installed it at his electrical panel on a 20 amp 2 pole breaker as instructed.

His july 2007 electric bill was 35%...yes ..35%.. lower than his july electric bill from 2006. He's not made any changes in his lifestyle or electrical demand by shutting things off or raising his thermostat. etc.

His electrical usage in KWH was OBVIOUSLY lower. The average temperature for july was 5 degrees cooler in 07 than in 06. But can't explain away the savings. Can you?

He will get his investment back quite soon. Then save $$$$ for 20 years. HAGD

[jraef]

He is either mistaken about "changes in his lifestyle" or had inadvertently fixed some other problem that he had but was unaware of. There is NO WAY that PFC capacitors saved that much energy, if any. Sorry. There are finite physics and electrical engineering principals involved here. Magic boxes have no basis in reality.

 

Anecdotal evidence without carefully controlled test conditions is essentially meaningless. I could make a similar claim about having saved gasoline compared to last year by looking at my driving record and gas purchases. That says nothing for the driving conditions that may completely account for the differences. For instance, you state thjat "average temperature for july was 5 degrees cooler in 07 than in 06". That may be true, but an average does not take into account when the temperature differences existed. If it was warmer when his AC was not running anyway, i.e. a couple of weekends when he was out of town, he may have saved energy just by not having his AC on when it was warmer on those days.

[kens]

Hi electrician3, My occupation is an energy management consultant, (yes jraef I am one of those “experts” ), most of my time is spent analysing data concerning trends in energy usage. I could tell you any number of reasons why your brothers energy bill is 35% lower than the same month last year. I am not going to because you have not given me enough data. What I will say is that it is NOT because of the capacitive device that was installed. If you are an electrician then you will understand the basic theory that we are discussing here. I am not going to replicate the discussion, you can find it here without looking too hard. The physics are quite clear, there is no miracle in this equipment.

 

edit: I tried to attach a couple of graphs to this post but no go. If someone can tell me a simple way to post graphs from excell I will expand my point.

 

Ken

[jraef]

...snip

 

edit: I tried to attach a couple of graphs to this post but no go. If someone can tell me a simple way to post graphs from excell I will expand my point.

 

Ken

 

You can post them as images (use pdf creator if you have it) to a file hosting service, i.e. I use photobucket.com (it's free). If you don't have Acrobat Pro to make your own pdf files, there are several freeware programs that will do it by adding a pdf "printer" to your programs such as Excel and Word. Look around for real free ones though, as some of them come with time limits or nagware that gets annoying after a while and is hard to get rid of.

 

Then once you get an image file to your file host, link to the image in your response dialog box using it's url by clicking on the wizard button that has a little picture of a tree on it.

 

Consultant eh?

http://www.kerstein.org/dilbert/dilbert_consultants_hourly_rate.jpg

[kens]

Ok here is a graph of monthly gas consumption. Part of the reason I was asked to look at it was the dramatic increase between 2005 and 2006.

 

Please note that I'm in the southern hemisphere so June to August are our winter months.

 

http://i175.photobucket.com/albums/w158/kenobulusmaximus/ScreenHunter_1-2.jpg

 

Understandably there was some concern over the increase in Gas costs. The gas is used for space heating purposes so we add some temperature related data called heating degree days to the mix and come up with this

 

http://i175.photobucket.com/albums/w158/kenobulusmaximus/ScreenHunter_2-1.jpg

 

As you can see there is a direct correlation between the heating demand and the gas usage.

What I am trying to explain is that you cannot simply compare a monthly energy use with the same time last year and expect to gain any worthwhile insight into the situation.

 

 

jraef, my butt wiggling goes for 49c/10seconds