New Transformer - Aluminum Windings?

[adamscb]

We had a transformer short out on us, and I'm trying to get a refurbished one here in a decent time frame. It's a 300kVA padmount, 4160v down to 480v. I'm not sure if the windings are aluminum or copper (doesn't say on the nameplate). I have some quotes together, but unfortunately the only ones we can get here in a decent time frame have aluminum windings. If I were to land copper wires on this aluminum transformer, would I need any special kind of lugs/connectors? I'm relatively new to the construction side of things.

Thanks in advance.

 

[jaggedben]

Probably you can land copper on it. Whether you can do that depends on the markings you see on the terminals and from your point of view has nothing to do with what the windings are made of.

 

[infinity]

Just ensure that the lugs are listed for copper and aluminum.

 

[paulengr]

Aluminum windings are a lot cheaper. You pay a 25% premium to use copper windings. Aluminum is almost the only thing you will find on the market. The only people that demand copper windings are mines because copper windings take the abuse a portable substation goes through better compared to spending it's whole life sitting on a concrete pad and some high duty cycle situations like manufacturing test stands for motors, transformers, etc. I know because I used to be the guy at a large mine purchasing a dozen 1000+ kVA transformers a year.

You are connected to the bushings and there is very little oxygen inside the tank. It's not generally a corrosive environment inside. If someone sold you on copper windings unless you know you need them for mechanical reasons you got ripped off. Just pay attention to the lugs. They are usually Al-Cu because utilities use all aluminum wiring and industrials usually use all copper wiring.

Electrical grade aluminum is far different and equal to or exceeds copper today except for resistance. It is much stronger, doesn't corrode as much, and doesn't get brittle with age. That is why virtually all overhead utility lines are aluminum or aluminum coated steel reinforced. In the transformer itself the manufacturer just adds turns or uses larger diameters to deliver comparable ANSI standard impedance whether the windjngs are copper or aluminum. The house wiring in the 1950s was just a construction grade aluminum made into wire. It is not the same as electrical aluminum.

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