How To Identify A Transformer's Winding Material?

[sgtan1]

How does one go about identifying a transformer's winding material?

Is it only possible to speculate by weight difference?

 

[Skogsgurra]

Do you have access to the winding? If so, the colour (you may have to cut or scrape some paint or insulation away) will tell if it is Cu or Al. I can't think of any other winding materials in an ordinary transformer.

Gunnar Englund

http://www.gke.org

 

[logbook]

How about measuring the winding resistance then changing the temperature to get the TC of the winding. You may not be able to get to the wire of the winding becuase they may have put flexible leads on the transformer with the joints nicely protected inside the outer protective layers of the transformer. This technique is used to see the temperature rise of winding (when you know it is a copper winding).

You would have to check on the TC of aluminium relative to copper to check the feasibility of differentiating between the two on this test.

 

[wbd]

This is kind of obvious question but did you contact the manufacturer?

 

[jraef]

Interesting approach. I wonder if there is enough TC difference between the 2 materials to be able to detect, or how much of a delta-t you would have to accomplish to see it? That might be problematic if its a big transformer!

The only way to tell by weight difference would be to have 2 identically rated units with the same cores to compare to.

Gunnar may have the only viable answer. It would seem to me tha you should be able to see the material at the point where it connects to the wiring terminals, unless its a really tiny transformer, in which case, why does it matter?

Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[logbook]

Sorry, TC idea doesn't work. My data book gives both materials as having a TC of 0.0039/degC.

 

[BJC]

Call some outfit that anayzes oil in transfromer. They don't normally look for metals but you can ask if they can detect metals. You might see something useful.

 

[jraef]

Actually, we have no idea as to what size transformer he was talking about. Only the big ones have oil.

Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[d23]

sgtan1

If I remember correctly you need to mix a small sample of the transformer oil with a household cleaner that contains ammonia. The fluid will turn blue if there is copper in it. You will need to shake it to make it mix and change color.

The problem is if the windings are aluminum and the cabling is copper you will get copper from the cabling.

I would recommend checking with the manufacture.

D23

 

[waross]

Can you please describe the transformer?
yours

 

[sgtan1]

Thanks for all the replies.

The transformer is a cast resin type 2MVA, 11k/433
Anyway I guess we just have to check with the manufacturer.

regards

 

[davidbeach]

Cast core transformers, at least as supplied in North America, seem much more likely to have copper windings than to have aluminum windings. Do you know the rated full load losses of the transformer?

 

[Vladpl]

I agree with davidbeach. It will be more likely that the transformer has been wound with copper instead of aluminium. Usually welding transformers consist of aluminium windings. Big distribution transformers have Cu. I have never heard of 2MVA transformer to have aluminium. I work for a transformer company where I design transformers and power supplies.

My question is why do you need to know what material was used to wind the transformer.

If you want to know if it has been wound with copper or aluminium you can try and calculate it by working out the resistance of the winding.

Formula: R= pL/A

Where R= resistance/metre , p=resistivity (ohm m),L= length in m, A= cross sectional area.

p for Copper = 1.68 x 10^-8
p for Aluminium = 2.65 x 10^-8

Therefore if it is aluminium the resistance will be greater. You will have to estimate/calculate mean turn of a coil to get yout L (total length in meteres) and you should calculate this fairly easy.

Hope this helps.

 

[stevenal]

The cross sectional area is generally unknown, and will not be the same for the two materials. Aluminum is less dense, and usually lighter for a given ampacity. But without knowing the volume of the core or insulation, this fact won't help much either.