Aluminum Transformer windings-Areva Transformers

[wfowfo]

Our Coop is bidding out some 1000 Kva 7.2/14.4 autotransformers (the usual "needed it yesterday" type of bid). We got a very attractive bid from Areva (formerly Alstrom) Transformers. The two things that concern us are that we have no experience with this company, nor with the aluminum windings they will be using. We do not have any engineers on staff.

Does anyone have any experience with Areva they would care to share? Also, are there any significant drawbacks to aluminum windings?

 

[teng22]

I would be surpised if you have any problems with Areva T&D as they are certainly one of the major transformer manufacturers. As you rightly say, they were formerly part of the Alstom group and their UK division was previously GEC before that. For more information on this company you could try starting at their T&D website

http://www.areva-td.com/static/html/TDE-AGF_NavPage-NavPage_StandardLeft_TDE_1019571445648.html?

I hope this helps

 

[electricpete]

Copper obvsiously costs more. Many companies and utilities have historically specified copper windings. I'm sure by far most people have a lot more experience with copper winding transformers since that is most of what's out there.

Some transformer manufacturers say copper and aluminum can now give equal reliability.

http://www.alfatransformer.com/coppervsalum.htm

http://www.uptegraff.com/faqs.html

I would say if you are in a bid process and some companies are quoting aluminum while others are quoting copper, it is not a fair bidding process.. If the spec did spec copper than Areva isn't meeting it. If the spec didn't spec copper, than ask the other company why they chose the more expensive copper route... maybe they have some info to share on why they don't like aluminum.

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[electricpete]

The concern about aluminum windings as I remember was that the windings would loosen over time (after all creep is an inherent property of aluminum). Then when a through fault occurs, forces could cause enough movement to cause a fault. It was enough of a concern that all transformers I worked with when I was in T&D at our utility were copper windings. Whether the concern has really vanished as identified in those links I don't know.

Also consider there may be some differences in efficiency among transformers. The link showed aluminium slightly lower I assume efficiency will be reviewed in the decision process.

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[dpc]

One consideration - for winding faults, damage to the transformer is generally much more severe with aluminum windings than with copper. Aluminum windings, when faulted, tend to "splatter" all over the place, causing core, adjacent winding, and tank damage. Copper windings tend to fail a little more gracefully and with less "collateral damage". With a major winding fault with aluminum windings, the odds are much higher that you will be looking at a complete replacement of the transformer, rather than a re-wind.

For "throw-away" distribution transformers, aluminum windings may make sense if your loss analysis shows them to be less expensive in the long run. But for a substation transformer that I cared about and would not want to have out of service for a long period of time, I would stick with copper windings.

 

[jghrist]

Are both primary and secondary windings aluminum?

Aluminum strip is commonly used for low voltage windings of distribution transformers. With strip windings, the forces are radial so there is less concern with movement. I would not be concerned with the use of aluminum strip for the secondary.

Primary windings are generally varnished copper or aluminum wire. One concern with aluminum wire, at least for smaller ratings, is the physical strength of the wire connections.