T
T.M.Haja Sahib
Guest
Sorry,I committed a blunder.
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.
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.
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
Your interpretation is not acceptable.:happysad:
Target efficiency=Maximum efficiency
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%.
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.
I accept what you say,because you are saying about the product of your own country.
Anyway,have a word with Jim.
As am I. Your point?J&P book is from Britain
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:and if you try find an American book of edition later than 2007 on the same subject,you may find pertinent information.
Note the words average loading.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
In the mean time here is a post from another thread Transformer Efficency Curves on the same subject
A modern distribution transformer has maximum efficiency between 50% to 75% of its loading.So it is beneficial to load it in that range.
But the 35% isn't a single point. It's average loading over a 24-hour period.The reason the US government set the target efficiency point at 35%,
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.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.
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.
But what is the mechanism? How does reducing I2R losses result in increased Fe losses?in transformer design, the core losses and the I2r losses effect each other in the trade offs.
:thumbsup: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.