Power factor correction experiment

[iwire]

Your one line retorts are more often vague than clear.Why can't you explain a bit how I am wrong?

I don't think I could have been clearer.


But OK, let me try to clear it up for you

I asserted pumps may use less current if the voltage is reduced

You said 'No, that violates the affinity laws'

You were shown that your own reference proved reduce voltage can reduce current.

At that point you came back with this.

You are correct.It is line voltage not motor voltage.But the current is also line current and not motor current.Unfortunately,motor voltages and motor currents were not displayed.

That is simply double talk, the fact is the line currents reduced due to voltage reduction.



Now earlier you asked what I mean by troll, I really doubt that you do not know but here is what I mean when I say it.

A troll is a poster who questions or dismisses the content of most all other posts yet provides little, or no proof of their own views. Often a troll knows the subject well yet pretends not to. The motivation being to stir things up, to irritate others etc.

This describes you pretty well, you say all the others are wrong but not once have you been able to bring any independent references to the forum to show that you are correct.


आप का दिन अच्छा बीते!

 

[T.M.Haja Sahib]

You must have missed the point I made in post #118.


For the cage motors I've dealt with, slip is generally 1% or less at rated load. To check, I looked at a pumping project we did with three 4-pole machines. Speed at rated power is 1493 rpm and, like yourselves, our supply frequency is 50Hz. You will thus deduce have no difficulty in deducing that slip in this case is below 0.5%. Voltage optimisation is generally deployed when the motor is running at lower that rated load meaning that slip is even lower. To take as an example the machine I cited, going from say 3/4 to 1/1 slip would result in a speed difference of about 0.1%. That's all. From my experience, and we do a fair bit in the water industry, measuring head or flow, far less their product*, to that level of accuracy would be a challenge.

I don't disagree with the curve you submitted but it relates to variable speed operation. Here we are looking at a fixed speed application.

*pump power is head times flow

I am afraid that you lost sight of our original purpose:To find out whether there may be any energy saving due to connection of a small capacitor across the terminals of a small pump motor in a residence.The energy saving, if any,would be undoubtedly small.So considering pump motor as a constant speed one,while affinity laws assert otherwise, may or may not lead us anywhere.This has to be explored further.

 

[T.M.Haja Sahib]

I don't think I could have been clearer.


But OK, let me try to clear it up for you

I asserted pumps may use less current if the voltage is reduced

You said 'No, that violates the affinity laws'

You were shown that your own reference proved reduce voltage can reduce current.

At that point you came back with this.



That is simply double talk, the fact is the line currents reduced due to voltage reduction.



Now earlier you asked what I mean by troll, I really doubt that you do not know but here is what I mean when I say it.

A troll is a poster who questions or dismisses the content of most all other posts yet provides little, or no proof of their own views. Often a troll knows the subject well yet pretends not to. The motivation being to stir things up, to irritate others etc.

This describes you pretty well, you say all the others are wrong but not once have you been able to bring any independent references to the forum to show that you are correct.


आप का दिन अच्छा बीते!

Okay,Okay.Please cool down.I will not mind if you call me a troll or what:I know who I am.I came to this forum for discussion of technical matters that I enjoy very much.I wanted share that joy with others in this forum.I hope you will begin to enjoy your online time with me as most others do (this thread has a 5 star rating).As for your statements

your own reference proved reduce voltage can reduce current.
the fact is the line currents reduced due to voltage reduction.

It has a definite reduction of power and that much is certain.
See the bypass mode in the table of reference.current increase with decrease in voltage.
Finally,
What do you tell by आप का दिन अच्छा बीते! ?

 

[Besoeker]

So considering pump motor as a constant speed one,while affinity laws assert otherwise

It asserts no such thing.

 

[Besoeker]

See the bypass mode in the table of reference.current increase with decrease in voltage.

Wrong way round. The line voltage decreases slightly as a result of the increased current.

You missed this it would seem:

You would expect the voltage to be marginally higher is save mode because the current is is less resulting reduced line voltage drop.

 

[Besoeker]

Your one line retorts are more often vague than clear.Why can't you explain a bit how I am wrong?

Wrong on a number of technical issues but your greatest wrong is in trying to tell others, who clearly have much more expertise in this field than you, that you know better. You don't.

You can learn from listening to those of us who have been there and done that.
It's your choice whether you do.

 

[iwire]

Okay,Okay.Please cool down.

Cool down?

I was not mad or heated in the least.

Finally,
What do you tell by आप का दिन अच्छा बीते! ?

I was trying to tell you have a nice day, I guess Google failed me.

 

[gar]

111117-1600-EST

Besoeker:

The ancestry thing was just a little side diversion. Since you are listed as UK I thought you might have some English connection, and there seems to be a lot old historical records from there.

Henry Ford in the early part of the 1900s tried to trace his ancestors and at that time was not very successful. Still there does not seem to be any new information. Scotch and Irish. Search henry ford ancestry . By the way the IEEE History Center considers Henry Ford as an early electrical engineer. Reference Michael N. Geseiowitz. This comment is just to get some validity for these comments on this forum.

Then I went on the tangent of Howard H. Aiken, quite possibly the first modern proponent of the digital computer. This led me to http://en.wikipedia.org/wiki/Thomas_J._Watson . Very interesting. Interesting how NCR played a part in both IBM and General Motors, and in an electrical sense.

For Aiken, himself, it was about 1935 that he said the way to build a computer was digital. He was laughed at and told it can not be done. See http://www.ideafinder.com/history/inventors/aiken.htm . Aiken was an interesting character, based on many different writings, and my own limited contact with him.

Another association I had with a person associated with the early development of digital computers was as a student in a class on symbolic logic taught by Arthur W. Burks. See http://en.wikipedia.org/wiki/Arthur_Burks .

What we are able to do today, communicating around the world, are in part a result of these early pioneering efforts. If these individuals had not been been involved there would have been others that would have performed their function.

.

 

[Besoeker]

111117-1600-EST

Besoeker:

The ancestry thing was just a little side diversion. Since you are listed as UK I thought you might have some English connection,
.

No problem.
It's a quite common misconception for English to be seen as synonymous with British. It isn't.
I'm British. Not English.

 

[T.M.Haja Sahib]

Cool down?

I was not mad or heated in the least.

No.You were mad at me.

 

[T.M.Haja Sahib]

Wrong on a number of technical issues but your greatest wrong is in trying to tell others, who clearly have much more expertise in this field than you, that you know better. You don't.

You can learn from listening to those of us who have been there and done that.
It's your choice whether you do.

I do listen.See your post#138 wherein you argued that slip of the motor changes too negligibly.But I stressed that with reduced voltage energy saving method,the speed (as well as water output in the case pump) changes appreciably.That i am right can be seen from the case study of Indian Bureau of Energy efficiency


ELECTRIC MOTORS
Bureau of Energy Efficiency,
(under Ministry of Power, Government of India)
Hall no.4, 2nd Floor, NBCC Tower,
Bhikaji Cama Place,
New Delhi ? 110066.

Indian Renewable Energy Development Agency,
Core 4A, East Court,
1st Floor, India Habitat Centre,
Lodhi Road,
New Delhi ? 110003
.
By
Devki Energy Consultancy Pvt. Ltd.,
405, Ivory Terrace, R.C. Dutt Road,
Vadodara ? 390007, India.
2006

Case Study-

Operation in STAR connection for under loaded motors
Industry / Sector Edible Oil manufacturing Plant

year of Implementation: 1995

Cost Benefit Analysis
_ Type of Measure: No cost measure
_ Annual energy Savings: 4560 kWh
_ Actual cost savings: Rs 18,240
_ Actual investment: Minor
_ Payback: Immediate

Principle
When motors are under-loaded, their torque requirement is less compared to that at
full load. Hence the impressed voltage required at the motor windings is less due to
less torque required.

'In Delta-Connection', the line voltage is impressed on each motor phase winding.
Whereas in ?star connection?, line voltage divided by _3 is impressed on each phase
winding.

When ?star? connected, the current drawn by the motor drops significantly, power
factor increase also takes place. Overall power saving is likely to be 10 to 20%
depending on the extent of under loading.

Background

In this edible oil (Vanaspati) manufacturing company, A 25 hp/18.5 KW motor was
driving a cooling water circulation pump. The electrical measurements in ?delta
connection? were as follows :
Voltage : 415 V

Current : 18.5 A

Power Factor : 0.505

Power Input : 6.72 KW

Speed : 1469 rpm

Considering the fact that the load was less than 30%, it was decided to operate the
motor in star connection.

Voltage : 415 V

Current : 9.5 A

Power Factor : 0.873

Power Input : 5.96KW

Speed : 1454 rpm

It may be noted that the current has dropped but the power Considering the fact that
the load was less than 30%, it was decided to operate the motor in star connection.

Note that the reduction in power from 6.72 kW to 5.96 kW is not only due to
reduction in motor losses, but also a due to reduction in speed of driven equipment.
---------
Do you also listen?

 

[T.M.Haja Sahib]

It asserts no such thing.

See post#151

 

[don_resqcapt19]

I do listen.See your post#138 wherein you argued that slip of the motor changes too negligibly.But I stressed that with reduced voltage energy saving method,the speed (as well as water output in the case pump) changes appreciably....
Speed : 1469 rpm ...

Speed : 1454 rpm ...

How is a change of a bit over 1% an appreciable change in speed?
All that study says is that you can reduce the motor voltage to make up for a poor design. Had the motor been properaly sized at the design stage, you would have been saving that energy from day one without any electrical changes.

 

[Besoeker]

I do listen.See your post#138 wherein you argued that slip of the motor changes too negligibly.But I stressed that with reduced voltage energy saving method,the speed (as well as water output in the case pump) changes appreciably.That i am right can be seen from the case study of Indian Bureau of Energy efficiency

Excellent!
You have succeeded in presenting a case that nicely demonstrates a couple of points that I and others have made and you didn't accept.

Remember your post #70 that you asked for comments on?

If h.p,power factor,and efficiency of the pump motor are known,it is possible to calculate the increased current X at reduced voltage without the capacitor

Now you have cited a report that shows reduced current at reduced voltage.

And the report also confirms what I posted in #118:

If the motor is not fully loaded, reducing the voltage will not appreciably affect the motor speed. Slip will increase but by very little.

And I gave you a real life example of this in #138. Which you don't seem to have taken on board.
So, no, I don't think you are listening.

You are being given much knowledge and experience and here.
Knowledge and experience that demonstrably do not have.
You should grasp the opportunity, make the most of it - and learn from it.

 

[T.M.Haja Sahib]

I do listen.See your post#138 wherein you argued that slip of the motor changes too negligibly.But I stressed that with reduced voltage energy saving method,the speed (as well as water output in the case pump) changes appreciably....
Speed : 1469 rpm ...

Speed : 1454 rpm ...

How is a change of a bit over 1% an appreciable change in speed?
All that study says is that you can reduce the motor voltage to make up for a poor design. Had the motor been properaly sized at the design stage, you would have been saving that energy from day one without any electrical changes.

Appreciably means to a noticeable extent.A change in RPM from 1469 to 1454 with a slip change of a bit over 1%.Contrast this with what post #138 states:''less than 0.1% slip,.constant speed operation of pump etc.,''Also see what that case study says in conclusion''Note that the reduction in power from 6.72 kW to 5.96 kW is not only due to reduction motor losses, but also due to reduction in speed of driven equipment.''It is clear that posts#138 is misleading.

 

[T.M.Haja Sahib]

Excellent!
You have succeeded in presenting a case that nicely demonstrates a couple of points that I and others have made and you didn't accept.

Remember your post #70 that you asked for comments on?


Now you have cited a report that shows reduced current at reduced voltage.

You are apparently in a hurry,I presume.:lol:
The case of reduced current at reduced voltage is proved for motors lightly loaded.It is altogether a different matter,if the motor is operating near full load.

And the report also confirms what I posted in #118:

And I gave you a real life example of this in #138. Which you don't seem to have taken on board.

See post #155.I want you to learn that energy saving by voltage reduction method depends not only on the reduction in internal losses of the motor but also on the reduction in the motor output (and hence reduction in water output in case of pump).If the case study in post #151 does not convince you of that, nothing else can.

 

[Besoeker]

Appreciably means to a noticeable extent.A change in RPM from 1469 to 1454 with a slip change of a bit over 1%.

It is almost exactly 1%. Actually, if you wanted to be pedantic and that's what you are being by calling 1% appreciable in this context, if you calculate it to a sufficient number of decimal places, you'll find that it is less than 1%.

Contrast this with what post #138 states:''less than 0.1% slip,

That was is for a real motor and very likely a much more efficient one. Its full load efficiency is 97.3%. What was the efficiency of the one in the brief non-technical report you cited?
Such high efficiencies are relatively common in the water industry - energy is one of the main operating costs.
For the same reason, a motor running at less than 30% loading would not be tolerated.

 

[Besoeker]

You are apparently in a hurry,I presume.:lol:
The case of reduced current at reduced voltage is proved for motors lightly loaded.It is altogether a different matter,if the motor is operating near full load.

See post #155.I want you to learn that energy saving by voltage reduction method depends not only on the reduction in internal losses of the motor but also on the reduction in the motor output (and hence reduction in water output in case of pump).If the case study in post #151 does not convince you of that, nothing else can.[/QUOTE]
Actually, the post in #151 makes my point rather well and renders your premise in post #70 invalid.
You would do well to take note of the sound and detailed technical information being imparted in this thread and you may learn something.

 

[iwire]

The case of reduced current at reduced voltage is proved for motors lightly loaded.It is altogether a different matter,if the motor is operating near full load.

Can you point to a single post in this thread that would dispute what I made bold above? Not one of us has claimed a reduction in current would result if a fully loaded motor has it's voltage reduced.

Again, going back in this thread you tried to claim a reduction in voltage to a motor always increases the current.

You were shown otherwise and are now trying to change the subject.

I want you to learn that energy saving by voltage reduction method depends not only on the reduction in internal losses of the motor but also on the reduction in the motor output (and hence reduction in water output in case of pump).

Why would you want us to learn a falsehood?

 

[Besoeker]

I am afraid that you lost sight of our original purpose:To find out whether there may be any energy saving due to connection of a small capacitor across the terminals of a small pump motor in a residence.The energy saving, if any,would be undoubtedly small.So considering pump motor as a constant speed one,while affinity laws assert otherwise, may or may not lead us anywhere.This has to be explored further.

And I'll this one again.
Show me where in the article you posted on the Affinity Laws where it makes any connection between voltage variation and speed variation for a motor running directly on a fixed frequency supply.