The T.M.Haja Sahib Transformer efficiency thread

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T.M.Haja Sahib

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Though it is pedantic,I want to stress that maximum efficiency does not occur at 100% loading per post#75 but occurs at 93% per post #82 and also I still stick with my point that the maximum efficiency of general purpose transformers is at 35% loading and the transformer discussed here does not belong to that category.
 
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Besoeker

Senior Member
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Though it is pedantic,I want to stress that maximum efficiency does not occur at 100% loading per post#75 but occurs at 93% per post #82 and also I still stick with my point that the maximum efficiency of general purpose transformers is at 35% loading and the transformer discussed here does not belong to that category.

How about you provide a reference to support that?

As it happens, I have on my desk The J & P Transformer Book. It's an 800+ page tome and is described in the editor's foreword thus:
"The J & P Transformer Book is regarded as the leading treatise on the Power Transformer and as such is an essential reference for electrical engineers concerned with design, installation, and maintenance of transformers."


Transformer efficiencies is covered in chapter 5 of this book. On page 118 there is a chart showing various efficiency curves for different ratios of full load Cu losses to Fe losses. The highest ratio given is 4:1. This, perhaps not surprisingly, shows maximum efficiency occurring at 50% loading. It would need an even higher ratio than 4:1 for your transformer to give max efficiency at 35% loading. Given that J&P, a comprehensive work, doesn't give ratios greater than 4:1 I'd be inclined to the view that anything beyond that wouldn't be very common and not really classed as general purpose.

FWIW, I have looked back at my efficiency calculations for one system we did which included a 500kVA transformer. The ratio there was 1.42:1.
And not hugely different to mike_kilroy's 1.17:1
 
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T.M.Haja Sahib

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J&P book is from Britain and if you try find an American book of edition later than 2007 on the same subject,you may find pertinent information.In the mean time here is a post from another thread Transformer Efficency Curves on the same subject
In 2005 the US passed an Energy Policy Act that required all general purpose transformers sold after 2007 to be designed to a target efficiency of a '24-hour average loading of 35%'.
There are also provisions, for non-general purpose transformers as well as large (i.e. >500kVA) units.
 

iwire

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Your interpretation is not acceptable.:happysad:

Than the solution is very easy.:)

You are at a computer connected to the Internet, use the search engine of your choice and find something to support your claims.

If you are correct the information will be out there at a transformer manufactures web site.
 
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T.M.Haja Sahib

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It does not mean the target has been achieved.

It is an achievable target because the maximum efficiency of a transformer can be designed to occur at any load above 0 to 100%.
 

iwire

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Location
Massachusetts
It is an achievable target because the maximum efficiency of a transformer can be designed to occur at any load above 0 to 100%.



So, by all means, drop a link to a manufactures web site that shows they sell a GP transformer with maximum efficiency at 35% loading.

It should be easy if they exist.:)

Google is wonderful, look at the things you can find.


http://electrical-problems.webs.com/
It is said about Electricity that it is a science whose first principles may not be understood without understanding the whole of it.With this in mind,I want to explore,by a series of articles, different areas of Electricity through quotes taken from various books on Electricity and through personal observation in an attempt to understand the first principles of Electricity by trying to understand the whole of it.You are also requested to send your articles for this purpose.
 
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T.M.Haja Sahib

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I accept what you say,because you are saying about the product of your own country.Anyway,have a word with Jim.;)
(By the way,your articles towards enhancing the understanding of Electrical science are invited.)
 
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Besoeker

Senior Member
Location
UK
J&P book is from Britain
As am I. Your point?

and if you try find an American book of edition later than 2007 on the same subject,you may find pertinent information.
I'm sure there equally good American books on the subject. Quite a lot of good things are American, Mrs B being one of them. But, I suppose your point is in relation to this from Jim D's post:
In 2005 the US passed an Energy Policy Act that required all general purpose transformers sold after 2007 to be designed to a target efficiency of a '24-hour average loading of 35%'. There are also provisions, for non-general purpose transformers as well as large (i.e. >500kVA) units
Note the words average loading.
That could be full load for 35% of the time and zero load for 65% of the time or an unvarying 35% load all the time.
Whilst both are quite improbable scenarios for a distribution transformer, they serve to illustrate that picking 35% loading as the best point for maximum efficiency would be inappropriate for the first of them.


In the mean time here is a post from another thread Transformer Efficency Curves on the same subject

The one where you posted this?
A modern distribution transformer has maximum efficiency between 50% to 75% of its loading.So it is beneficial to load it in that range.
 

jim dungar

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The reason the US government set the target efficiency point at 35%, is because of all of the energy being wasted by oversized (too much extra capacity) transformers installed in the US.

Irresponsible designs regularly wasted precious resources by ignoring the actual 'losses vs loading' of their installations. They bought into the idea of reducing I?r losses in the conductors at the expense of no load losses.
 

Besoeker

Senior Member
Location
UK
The reason the US government set the target efficiency point at 35%,
But the 35% isn't a single point. It's average loading over a 24-hour period.
You'd need to have a 24-hour load profile to work out what the optimum design was for least energy losses over a typical 24-hour period.

Irresponsible designs regularly wasted precious resources by ignoring the actual 'losses vs loading' of their installations. They bought into the idea of reducing I?r losses in the conductors at the expense of no load losses.
No-load losses are primarily Fe losses. I don't quite see how reducing Cu I2R losses would or should increase Fe losses but I'm not a transformer designer.
Maybe you could explain?
 

mike_kilroy

Senior Member
Location
United States
in transformer design, the core losses and the I2r losses effect each other in the trade offs. bottom line is a transformer is a 98-99% efficient gidget; as previously stated, typical designs can make the i2r portion 1-4x the core losses; the net result will still be a 98-99% efficient transformer. My 400kva had 8500watts losses, about 4000 from core, 4000 from i2r; we actually did redesign this one for the next machines to reduce the cose losses to 3000-ish and i2r bumped up to 5000-ish - in order to reduce nema enclosure temperature since 90% of its life is spent near idle on this carbon fiber tape laying machine so encl only gets really hot the short time they load it to the full capacity. Reducing one definitely increases the other.

on the same eff topic, if one studies the eff levels and core and i2r losses for the many transformers listed in TMs reference pdf, one sees it is not uncommon for designs to actually be more efficient at full load than lower. TM's fixation on "transformer efficiency" as % of rated size is the problem I see; it has very little meaning! so he shows that transformers can be twice as efficient at some level than others, when in reality we have all pointed out to him this is useless information. the efficiency of power out vs power in is what counts, and when looking at real transformers at real loads, one sees the difference in efficiency is only typically 0.3% so meaningless.
 
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templdl

Senior Member
Location
Wisconsin
in transformer design, the core losses and the I2r losses effect each other in the trade offs. bottom line is a transformer is a 98-99% efficient gidget; as previously stated, typical designs can make the i2r portion 1-4x the core losses; the net result will still be a 98-99% efficient transformer. My 400kva had 8500watts losses, about 4000 from core, 4000 from i2r; we actually did redesign this one for the next machines to reduce the cose losses to 3000-ish and i2r bumped up to 5000-ish - in order to reduce nema enclosure temperature since 90% of its life is spent near idle on this carbon fiber tape laying machine so encl only gets really hot the short time they load it to the full capacity. Reducing one definitely increases the other.

on the same eff topic, if one studies the eff levels and core and i2r losses for the many transformers listed in TMs reference pdf, one sees it is not uncommon for designs to actually be more efficient at full load than lower. TM's fixation on "transformer efficiency" as % of rated size is the problem I see; it has very little meaning! so he shows that transformers can be twice as efficient at some level than others, when in reality we have all pointed out to him this is useless information. the efficiency of power out vs power in is what counts, and when looking at real transformers at real loads, one sees the difference in efficiency is only typically 0.3% so meaningless.

Mike, I agree with you that this may be "Much To Do About Nothing," Fear less, hope more, eat less, chew more, whine less, breathe more, talk less, say more, hate less, love more, and all good things will be yours. ~swedish proverb~
The biggest complaint that I ever have had was as to why a facility was still using power having to pay an electric bill when their facility was shut down without knowing that their transformer still being energized with NL.
 

Besoeker

Senior Member
Location
UK
in transformer design, the core losses and the I2r losses effect each other in the trade offs.
But what is the mechanism? How does reducing I2R losses result in increased Fe losses?


bottom line is a transformer is a 98-99% efficient gidget; the efficiency of power out vs power in is what counts, and when looking at real transformers at real loads, one sees the difference in efficiency is only typically 0.3% so meaningless.
:thumbsup:
No dispute with that.
 
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