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Power Factor Controllers


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#1 marke

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Posted 17 May 2002 - 01:29 AM

For a paper on the power factor controller energy savers (Based on a NASA algorithm) have a look at Energy Savers, are they a sham?
The technology works, but it is well over stated and over sold.

#2 Sienna

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Posted 02 July 2002 - 11:50 AM

I have read your paper with interest. I work for a company who sell such controllers.

A lot of your comments are unduly negative, however I do agree that in the general marketplace I have seen some of our competitors sell controllers and fit them to any old application and mislead the savings made.

We have one of the only controllers on the market (Globally) that can control succesfully (for example) Injection moudling machines where it is common to go from 20kw off load to 150kw full load within 1/150th of a second. We have hundreds of blue chip companies as customers, and Jaguar have hundreds of our units on site.

I would wholly appreciate you re-writing the report, and place positive aspects of motor controllers also to create a balanced view as your opinions are somewhat biased for some reason.

We have had scores of independant tests done on our product which show undoubtedly the savings made which include thermal imaging on motors with & without our product, and we have the only product that is truly intelligent.

I am the first to agree, we have some poor quality competition in the market and we are doing our best GLOBALLY to promote a truly unique and world class device as our own.

I look forward to your reply.

#3 marke

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Posted 02 July 2002 - 08:17 PM

Hello Sienna
I am sorry that you find the report so negative. In my book, the bottom line is that You Can only save PART of the energy that is being WASTED. If the motor is operating well below its maximum efficiency for significant periods of time, energy can be saved. There is no argument about that, and that is clearly stated. My negativity is towards some of the claims made in the market place. I do clearly state that the technology works. If you have any particular areas of the report that you have problems with, perhaps you could let me know.
:)

#4 Harry Dampers

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Posted 03 July 2002 - 02:16 AM

C'mon Siena ...surely you must admit that there are very few loads that will benefit from so-called energy savers .

Yes, the Intermittent loads where power consumption jumps from zero to full load in a fraction of a second is one of them .

But you could also argue that even in installations where these loads predominate ......you may be better off economically putting in some fast acting Thyristor PF. correction which will then control the total PF of the plant or section of the plant .....as opposed to at individual motors.

I am pretty sure that it would be cheaper (for example ) to put one common PF controller to correct lets say 10x 55kW motors operating intermttently ............than to install 10 ...Soft Starts with energy saving .......and it seems that if you need to go from no-load to full in 150th of a sec ......then you hardly need a Soft start.

If you have a Motor that runs for long periods unloaded ......then perhaps it is better to use the best energy saver of all ........switch it off.

I get the distinct feeling from talking to R+D people in Starter manufacturing companies that they include is feature mainly so that are not the odd men out .........rather than because it is a useful feature.

#5 GGOSS

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Posted 03 July 2002 - 06:39 AM

Hi Siena,

I must say that I fully agree with most comments made by both Mark and Harry on this subject......but I am also prepared to give you the benefit of the doubt.

Unfortunately my experience with people marketing such products is that when they are asked the 'hard questions' they do not respond by providing proof of their claims. In fact most simply don't respond at all!

You appear to be very passionate about this subject and you have also made comment about other lesser products currently available on the world market.

I am providing you with an opportunity to establish some credibility and tell the forum why your product out-performs all others. Please ensure that you support any claims with technical facts.

Looking forward to your reply.

GGOSS

;)

#6 Sienna

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Posted 03 July 2002 - 09:20 AM

Thank you all for your comments.

I will provide independant technical test reports of our product, by I will need an E-mail address to send them to. I will also next week send details of the Thermal Imaging tests we performed.

#7 Sienna

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Posted 03 July 2002 - 09:32 AM

Replies to each person now!!

To GGOSS

>>Unfortunately my experience with people marketing such products is that when they are asked the 'hard questions' they do not respond by providing proof of their claims. In fact most simply don't respond at all!<<

I have seen it a lot, its generally because they are poorly trained or are just looking at the wrong applications or trying to make a fast buck.

To Harry Dampers,
>>C'mon Siena ...surely you must admit that there are very few loads that will benefit from so-called energy savers<<

No, there are thousands of applications worldwide. In our company experience the "Best" ones are Injection moulding machines (we have an approval from Mannesman Demag!!) Granulators, Crushers, Compressors, Vac Pumps and anything else that has a motor overated for the job of work its doing.

>>But you could also argue that even in installations where these loads predominate ......you may be better off economically putting in some fast acting Thyristor PF. correction which will then control the total PF of the plant or section of the plant .....as opposed to at individual motors.<<

Yes, you could argue that but you still have no control over the motors. It is common to install a controller where the site already has PF correction.


>>I am pretty sure that it would be cheaper (for example ) to put one common PF controller to correct lets say 10x 55kW motors operating intermttently ............than to install 10 ...Soft Starts with energy saving .......and it seems that if you need to go from no-load to full in 150th of a sec ......then you hardly need a Soft start<<

What happens under Star Delta starting?? upto 20 times initial running current is pulled into the motor. I have seen drive trains sheared because of this. We can also soft start any torque changes in the motor if required, this is particularly useful on compressors with large accumulators fitted. This significantly prolongs the life of the system. If the motors you suggest were operating intermittently then i would agree with you, ther would not be a significant return on investment. Ideally for our product you need a motor to run at least 18 hours per day & 5 days per week. We do however look for 24/7 applications.

>>If you have a Motor that runs for long periods unloaded ......then perhaps it is better to use the best energy saver of all ........switch it off.<<

Our unit can be set up to switch off the motor automatically after a pre-determined period of no load. I have been to thousands of factories where motors are just running for no reason.

>>I get the distinct feeling from talking to R+D people in Starter manufacturing companies that they include is feature mainly so that are not the odd men out .........rather than because it is a useful feature.<<

We sell Soft Starters under 7.5kw and mention any energy saving will be a bonus. However, 11kw upto 900kw are sold as pure energy saving devices with a whole host of additional benefits.


I have writers cramp now!!, if someone can indicate which E-mail address they would like further information on our product I will gladly send it next week. I am out of the office Thursday & Friday.

With Kind Regards

#8 marke

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Posted 03 July 2002 - 10:24 AM

I for one would be interested in seeing any information that you have. My email address is empson (at) lmphotonics (dot) com
;e

#9 marke

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Posted 04 July 2002 - 08:53 PM

I think that perhaps the point of most interest here, is not whether the technology can save energy under the right conditions, that is not in dispute, but can the energy saved jsutify the expense in terms of money saved and the cost of saving it. Would you spend $1000 to save $10 per year?? you may be better to put the $1000 in the bank and earn interest!
;q

[Edited on 4/7/02 by marke]

[Edited on 4/7/02 by marke]

#10 GGOSS

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Posted 09 July 2002 - 06:43 AM

Hello Sienna,

In previous posts you have stated that it is the technology used in your product that makes it a much more affective energy saving device than others presently available on the world market.

Without revealing any 'trade secrets' can you enlighten us further on the technology being used and how the product operates in a 'real world' applications?

I am interested to know more, as are other members of this forum.

Regards,
GGOSS

#11 marke

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Posted 05 August 2002 - 09:20 PM

I would like to summarise the data that I was submitted as follows.
Tests done on a 15KW motor.
At full load (15KW), the power consumed was 18.57 KW.
At half load, (8.9 KW) power input was 11.44 KW.
At no load (0.4Kw) the power input was 8.3KW.

Savings at half load were about 1KW (9.71%) and at no load the savings were about 3.5KW (41%)

The problem that I have with these results is:
At full load, the total losses are in the order of 3.5KW, and at half load, about 2.5kw and at no load, the total losses were a whopping great 7.9KW

My understanding of induction motors shows that the iron loss is essentially constant (independant of load) and the copper loss is dependant on the current squared. I would expect that the iron and copper loss at full load are in the same order of magnitude and constitute the greatest proprtion of the lotal losses. I am unable to see why the energy wasted at no load is so much higher than at full load or at half load. In this case, I would expect that the no load energy losses would be more like 2 KW, and assuming that the quoted percentage saving was correct at about 38%, this would result in an energy saving of about 760W. What is the pay back period??

I have been looking for a mechanism for the increased losses at no load, but to date, none has been forthcoming.
Any thoughts??
;q

#12 electricpete

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Posted 11 August 2002 - 03:47 AM

I agree with you Mark. The 8KW loss at no-load is not realistic.

#1 - There is no physical basis for explaining rapidly increasing losses as power decreases.

#2 - If the motor is sized to handle 8kw of losses but has only 3kw at full load, then shouldn't the motor rating be much higher? Simply doesn't make sense.

#3 - I have reviewed motor test data and never seen any results similar to this.

#13 gbasturk

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Posted 20 September 2002 - 10:59 AM

Dear Sienna,

I would appreciate it very much if you can inform me about the website or contact information for the company which sells Power Factor Controllers that you work for (you have mentioned (
QUOTE
Originally posted by Sienna
I have read your paper with interest. I work for a company who sell such controllers.
)

Yours sincerely
Gokalp



[Edited on 9/11/02 by marke]

#14 indigo

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Posted 02 October 2002 - 01:16 PM

Hi Sienna,

I love to get more detail about your product which make great energy saving on induction motors.

Thanks
CSS

#15 mmy123

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Posted 06 January 2003 - 03:46 PM

Hi Sienna,

Need more detail about your product which make great energy saving on induction motors. How it work ?
any website ?

Thanks

#16 Area

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Posted 18 August 2003 - 09:38 AM

Dear Marke,

I am currently dealing with the same question for our company and I am very interesseted in the results of Siennas example.

I am not an expert in this issue, but I am missing one thing in all posts that I have seen so far (also in other forums): The distinguishing between active power (kW) and reactive power (kVAr).

Is seems to be undoubted, that energy can be saved with a soft starter. I think (almost) everybody will agree to this statement. The question is only: How much and what is the benefit?

In my opinion, the most part of the power that can be saved with a soft starter is reactive power (kVAr). In our case (and maybe also for many other customers), this is not interesting, as we do have power factor compensation units installed that are suitable to compensate to almost 0.99. So the saving in kVAr that might be achieved is not interesting. More interseting for me is the savings in active power (kW), because that is for me the real benefit.

Therefore it would be interesting to know, what is that part in the example of Sienna? I think that the savings that you mentioned in your last post is not 8.3kW for 0% load, but 8.3 kVA. I assume that most of this 8.3kVA is kVAr and therefore not really intersting for many customers.

;p;

#17 marke

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Posted 18 August 2003 - 10:36 AM

Hello Area

Welcome to the forum.
Firstly, I wonder if you have read the paper on this site about the energy saving systems, claims etc. If not, you can read it here : http://www.lmphotonics.com/energy.htm This may help to answer some questions for you.

QUOTE

energy can be saved with a soft starter

No, I don't agree. Only some soft starters have an energy saving option, so without this option, you will not save energy. Some manufacturers and/or sales people promote that you will save energy because the start current is reduced, but a reduced current for a longer time can actually equate to a higher energy consumption. You will not save energy during start, just use it at a slower rate.
If the energy saving option is included, then there is a possibility to save energy, provided that the motor is operating for a considerable period of time at a considerably reduced efficiency. That requires the load to be very small for a reasonable percentage of the operating time. (typically less than 30% shaft loading before any saving will be achieved)
The amount is of course dependant on the amount being wasted. Large motors are very efficient with iron losses of 2 - 3 % of their rating so very small amount to save. Very small motors are more inefficient with losses more in the order of 10 - 15% of the motor rating so there is more potentially available (wasted) to save, but in nearly all cases, the actual watts that can be saved are very small relative to the rating of the motor.
Under very light loads, especially open shaft, there can be significant reductions in the KVAR drawn by the motor, but this should be tempered with the fact that the remaining current can be heavily distorted which introduces other harmonic losses in the system, offsetting some of the apparent gains.
Bear in mind also, that this KVAR reduction occurs only when the motor is under extremely light load, so it is not a substitute for power factor correction.

The example supplied by Sienna was actually as I stated an electrical loading of 8.3KW for a shaft load of 0.4KW. These are the figures given and they do not ring true to me as previously explained. The total losses of a motor are highest at full load, and lowest at zero load. The quoted example showed losses reducing from full load to half load, but more than doubling from half load to zero load. That just does not happen so I say that there is an error in the example and it does not hold water.
We had some private communications in this regard, but the subject/question was never resolved.
Best regards,

#18 Area

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Posted 18 August 2003 - 11:42 AM

Hi Marke,

it seems I did not make myself fully clear. I read your paper (good work by the way) and I fully agree with you, that you can only save energy that is wasted. I also fully agree with you, that you can only save energy with a softstarter on a motor that is running on a (very) light load and of course only if it is equipped with this energy saving function. My statement was meant that way (thanks for correcting me).

But it seems to me, that we can agree, that under this circumstances (light load < 30%), a softstarter (equipped with this energy saving function) can save energy. The key question for me is, what type of energy can you save (active and/or reactive power) and how much.

As explained in my last post, the difference between active and reactive power is very important for me, as I (in our case) can only save money with on active power, but not on reactive power. It seems to me, that people usually write kW, but really refer to kVA (U*I*SQR(3)).
I read several application reports of these soft starters, and they usually pretend to modify both, the efficiency and the cos PHI.

I also enclose a report that I found on one manufacturers web side. I tried to understand it but did not succede. Maybe you can give me a comment (for both, my calculation and their claims). If I understood everthing right and assume that the motor had the same mechanical output after the optimization than it had before the optimization, it would have an efficiency of 106% after the optimization:

Motor before optimization:
Motor takes 50,2kVA from the net (75kW * 47% load / efficiency 92.8%/ cos PHI 0,75)
This can be split in 37,7kW active power and 33,2 kVAr reactive power (cos phi = 0.75)

Now a soft starter is used to optimize the energy consumption. In my opinion, the soft starter can not go beyond the limit of the motor, which is the data at 100% load: Therefore, the max. achievable efficiency would be 94.5% and the max. achievable cos PHI would be 0.84.

After optimization:
Motor takes at its best 44kVA from the net (75kW * 47% load / efficiency 94.5% / cos phi 0.84)
This can be split in 37kW active power and 23.9 kVAr reactive Power (cos PHI 0.84)

It is not clear to me, if and how a soft starter can achieve it; I just assume that this is the technical limit that can be reached.

The result in this case would be: Saving of of 9.3 kVA which sounds very nice. In fact, these 9.3 kVA are app. 9.2kVAr reactive power and 0.7kW active power. Assuming that a power factor compensation unit is allready installed, the possible savings for me are not 9.3kVA but 0.7kW only.

An ideal motor (cos PHI = 1, efficiency 1.0) would take 35kVA = 35kW from the net. (75kW mechanical power * 47% load). In this case, the actual power that is taken from the net (manufacturer pretends 33kW) is smaller than this value. That I do not understand, except if the mechanical output is less after the optimisation. But then the calculation of your energy saving is no longer valid, because you compare two different mechanical output powers.

#19 marke

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Posted 18 August 2003 - 07:37 PM

Hello Area

The energy saving concept is to reduce the voltage applied to the motor when it is operating at less than optimum efficiency in a manner to cause the operating efficiency to increase.
Reducing the voltage applied to a motor will reduce the magnetising current (inductive) and the iron loss (resistive) but will increase the work current (resistive).

So the bottom line is, yes there can be a reduction in both the KW and the KVAR. Under part load conditions, it is also possible to have a net increase in KW with an effectrive increase in copper loss due to the increased "load" current.
As you are only interested in KW savings (as most people are) the savings are generally very small relative to the motor rating and are highest on small motors at zero load. Many of the marketers involved in this technology quote percentages rather than watts, and you can save say 40% of the open shaft losses of the motor, but this is still very small relative to the motor rating.
Please rest assured, I do know the difference between active and reactive power. All the figures that I quote and use are true KW figures (active power), not KVA. I can not vouch for some manufacturers figures though.

If you are looking to justify the use of the technology based on watts saved, only look at small motors operating 24/7 with significant amounts of time open shaft. i.e. punch presses, plastic granulators etc.

In terms of your quoted example, my comments are:

  • At 47% load with a 75KW motor, I would not expect to se any saving at all, certainly no significant saving
  • In my opinion, you will not increase the efficiency above the rated full load evviciency, and I would not expect to equal it.
  • I would not expect the power factor to exceed or equal the rated full load power factor
  • You can not calculate the power consumed when the energy saver is operating based on measured voltage, current and power factor. The current in non sinusiodal and the normal formula do not work.
  • Results must be measured on quality 3 phase metering equipment designed to operate with non sinusoidal waveforms.

      I believe that you are right to question data claimed for many of these applications. Much data that I have seenover the years has been obviously "created" by people with a very poor technical understanding.
      If we look briefly at the motor quoted, 75KW with a maximum efficiency of 94.5%, then at full load, the losses would be in the order of 4.3KW Of this, I would expect about half to be iron loss, say 2 - 2.5KW and under very light load conditions we may say 40% of this which is going to be in the order of 1KW. As the load is increased, the power saved will reduce.
      I would never consider or expect to get real power savings unoless the load is light and the efficiency is low. I usually use a power factor of less than 0.4 as an indicator that there may be some potential to save energy.
      I would expect that the figure of 0.7kw is very unlikely based on the above.
      Best regards,

#20 risktkr

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Posted 13 March 2005 - 03:04 PM

HAs any one reviewed the products sold by SOMAR? The Power Boss? The savings claims seem to be optimistic.




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