Amorphous Cored Transformers 1

[prc]

During 1980's many transformer manufacturers went for high efficient ,amorphous cored distribution transformers .No-load loss reduction of 60-70% was claimed.But it seems in later years interest in amorphous cored transformers came down ,may be due to cost (?).What is the current status all around the world for this type of transformers ?What is future of this technology ? Is amorphous cored distribution transformers popular in US and europe?What are the advantages and disadvantages of these transformers ?

 

[RalphChristie]

prc:

I have seen in the J&P Transformer Book (12th edition - Martin Heathcote) some comments regarding amorophous steels in transformers. Some quotes from this book:

Originally developed by Allied Signal Inc., Metglas products in the USA, in the early 1970s. The importance of their magnetic properties was first recognised in the mid-1970s. Although still restricted in their applications some 20years later due to difficulties in production and handling, they offer considerable redution in losses compared to even the best conventional steels.

The original developers of this material, Metglas Products, had towards the end of the 1980s produced a consolidated strip amorphous material named POWERCORE[®] strip, designed to be used in laminated cores. The material is produced in the thickness range 0.125 - 0.25mm, by bonding several sheets of as-cast ribbon to form a strip which can be handled more easily. The ribbons are effectively bonded over 15-75% of their surface area by a local plastic combined with a chemical bond of silicon oxide. The weak bond does not allow significant eddy current flow between layers of the composite.

The need for a glass-forming element, which happens to be non-magnetic, gives rise to another of the limitations of amorphous steels, that of low-saturation flux density.

While the sizes of strip available as POWERCORE[®] are still unsuitable for the manufacture of large-power trsf cores, in the USA in particular, many hundreds of thousands of distribution transformer cores with an average rating of 50kVA have been built. In Europe use of the material has been a far more limited scale, the main impetus been Holland, Sweden, Switzerland, Germany and Hungary. One possible reason for the slower progress in Europe is that the thin strip material does not lend itself to the European preffered form of core construction, whereas the wound cores, which are the norm for distribution transformers in the USA, are far more suitable for this material. In the UK its use have been almost exclusively by one manufacturer - but report that the difficulties of cutting and building this into a conventional core can tend to outweight any benefits gained.

Another of the practical problems associated with it is its poor stacking factor which results from a combination of the very large number of layers of ribbon needed to build up the total required iron section and also the relatively poor flatness associated with this very thin ribbon. Stacking factor between 0.8 and 0.9, but it is poor compared to the 0.95 - 0.98 attainable with conventional silicon steel.

 

[edison123]

Good post Ralph deserving a star.

I never bought that "significant reduction in loss" in amorphous core thing when a good trafo efficiency is as high as 99% and the no-load losses are no greater than 30% of total loss.

They had their day and made their money. Just like ISO craze, this was just a fad.

Of course, others are welcome to haul me over the fire on this.

 

[prc]

Thank you RalphChristi and edison123. Apart from manufacturing details ,the query is whether to day distribution companies are really going in for amorphous cored transformers?It is understood that some reputed leaders in transformer industry in US and Europe closed down their amorphous lines many years back due to commercial and technical reasons.So was it only a fad as edison said or in some regions are these ''super efficient" trfs still being used or rather purchased ? Even in wound cored trfs ,with amorphous core, though iron loss may come down by 60 % ,copper loss will go up due to poor space factor .Unless the utility follows a skewed capitalisation formula,ie very high un natural iron loss rate and very low copper rate (as low as 1/9 th) ,amorphous core seems to be unviable and fail to justify its high first cost.So what is the current position in US,Europe,South America,China,South Asia or Australia with regard to Amorphous cored trfs?

 

[Skogsgurra]

I have a friend that is producing transformers with low no-load losses. It is being used as a distriburion transformer in areas where loads are very intermittent (like recreational areas with high loads during holidays and week-ends and very low load during the weeks).

The no-load losses are important in such situations since they have a great influence on the total energy lost over a year.

The transformer is built with normal transformer plate but it is designed to be completely symmetrical - magnetic flux is the same for all three phases - and this makes the total iron volume smaller than if you use a "three-in-a-row" transformer design. Also, the flux density is more uniform. You do not have to design for the magnetic bottlenecks and that also reduces total iron volume.

If flux is kept the same, the iron losses are proportional to iron volume - and if the volume is reduced, so are the no-load losses.

There is a home-page on

http://www.nordtrafo.com/index.asp

Sorry that it is only in Swedish, but you can see how the symmetric geometric design is reflected in the shape of the container.

 

[Skogsgurra]

distriburion = distribution

 

[RRaghunath]

In India, I am seeing these amorphous cored transformers on road sides installed by local power distribution company for the last couple of years.

One difference I find when I look at these transformers is that they look short and stout compared to conventional transformers. I do not know the reason and would like to find out.

As Skogsgurra pointed out, these transformers have future in the distribution segment alone (that too if the volumes succeed to drive down the cost), I think.

 

[prc]

Rraghunath,What you mean by "short and stout ".It means circular in shape and less height ?If so ,it is not a characteristic of amorphous cored units .It only means single phase pole mounted units with wound core ,material can be CRGO or Amorphous core.I found a contribution in a recent book from US " Electric Power Transformer Engineering " -Edited James H Harlow ,CRC Press ,2004 .Under Distribution trfs (chapter 2 ,page 2-62 )
"With the movement to deregulate electric utilities in the US, most utilities have now chosen to neglect elements of system cost (in the calculation of loss capitalisation formula )that no longer may apply or to abandon entirely the consideration of the effects of transformer losses on the efficiency of their distribution system .Typical loss evaluation factors in the year 2003 are A= USD 2.5 /W and B =USD 0.8 /w "(Iron loss and copper loss factors )In such a scenario , amorphous core seems to have not much future.Of course,as rraghunath said ,in India and Bangladesh amorphous cored trfs are still being made in large numbers,but other parts of globe,it is going out of circuit ,unless ofcourse,someone with knowledge contradict it.

 

[RRaghunath]

prc,

No, the transformers are not circular. They are rectangular only but, looking at them, I felt the transformers are short with larger width and depth than conventional ones.

These are definitely amorphous cored ones (it is written so on the body of the transformers).

 

[stevenal]

prc,

My company evaluates loss prior to the bid award. Losses are given dollar values which are added to the purchase price prior to choosing low bid. These factors are a stab at estimating the cost of losses over the life of the transformer. To date, no manufacturer has found it cost effective to bid an amorphous unit. Efficiency is good, but what's the payback?

 

[prc]

Stevanal,All around the world,most of the utilities are evaluating bid as mentioned by you.But some utilities are putting extremely skewed rates eg USD 6600 for NLL and USD for 750 for LL for single phase trfs 10-100 KVA .In such situations ,amorphous core is the only option.Can you share the rates followed by you for such distribution trfs and the country referred to.What is the trend over the years and the reason for the same.

 

[edison123]

Me thinks, amorphous core supports the theory of diminishing returns. Unless its cost is brought down to CRNO levels, it is a goner in today's "competitive global economy".

 

[stevenal]

I don't have our factors handy, but I am sure they most be lower. I'm in the western USA.

 

[mc5w]

I asked somebody at ABB about it and he says that amorphous is dead. Nobody was able to get the production cost down to a reaonable level and nobody was willing to pay extra for the lower losses.

Modern conventional transformers are so efficient at low loads that you do not save very much evne with a distribution transformer.

The real dark horse is conductive polymers. A conductive polymer that can carry 3 times as much current as copper and only dissipate the same amount of heat would kill off superconductors. Superconductors have a tremendous no load loss because of the refrigeration equipment.

 

[mc5w]

I also forgot to add that the production cost problem was similar to how the guy who really invented the silicon transistor was a chemist over at Dupont who figured out a cheap way to refine silicon to a natural impurity level of 1 part per billion. Otherwise, we would still be making vacuum tube televisions.