Aluminium vs Copper Transformers

[Paul.]

Back in the 1970s before the term "buzzbox" was invented I bought a 140 amp air cooled arc welder, a mate borrowed it and was so impressed he bought one too, his turned out to be rubbish, it kept overheating, blowing fuses, and a completely different feel to the arc, when we compared them his was half the weight of mine so we took them apart, turns out mine has a copper wound transformer, his was aluminium, I still have mine it still works as well as ever, the other one was scrapped after a year or so.
Having said that though, I've used loads of different welders over the years, many with ally transformers that have worked perfectly well, usually they have decent cooling fans though.

 

[brightspark]

I Will refer you to an old post I made about my old buzz box, it is made from Aluminium and still going strong even though its just a little bit erm battered
http://www.mig-welding.co.uk/forum/showthread.php?t=8879

me bruv has a 120 amp clarke arc welder bought cheap with aluminium tranny. its very portable and ok for laying one rod on if u give me your addy eil il send u a new green welding glass free if u cant aford one wish i could weld as good blind

 

[eil]

I don't use that mask BS, that was the original that was supplied with the welder, but as you can see it did get some work, and my eyesight was better then,I weld by Braille these days

 

[SirDick Diodenob esquire]

I agree with whats already been said about the disadvantages of Aluminium but I also agree with GeorgeB that with a well made welder you wouldnt tell the difference . The only reason for using Aluminium as far as I know is economic and all I have seen by the use of it over the years are big problems . There was a manufacturer of air circuit breakers used aluminium finger contacts in the early 1980s , it cost them dearly they were a world market leader who should have known better , they withdrew the design and have not repeated the mistake . When an aluminium transformer blows it splatters the windings all over the inside of whatever cubicle its in, at least with copper its a less messy clean up . The theft of copper especially on railway lines and substations is getting out of hand despite better security methods , I think its inevitable that Aluminium will make a comeback at some point as the price of copper is only going to continue rising faster than other metals.

 

[rowan]

winding a transformer

i'm winding a transformer out of a telwin 201 welder from the 90's it's wound from aluminium and it fryed. i'm going to wind it with copper . the original winding's are 2.3mm aluminium and i'v bought 2.36 copper . do i wind it the same amount of winding's . i don't mind if it increases the amps as i'm building a new bridge rectifier using 4 100 amp three phase diodes .

 

[shenion]

Yes, use the same number of windings.

With copper, you will get a better duty cycle and probably a bit more top end current.

Copper resistance is about 60% of copper. So there will be 40% less heat at the same current.

 

[KemppiFrog]

Just looked at this thread ( Strickly bores me skull-less) And I agree about copper working better than ally. For a simple buzzbox, how different can the wiring be? I had a clunky Portuguese built ally wound 180 that suddenly quit. As I was in the middle of an important job, I called the B&D guy. He had shown me a 160 as a demo cut price job a few day previous. He put it on the bus, and I had it that evening. Now, it was copper wound and it was much nicer than than the ally job to use. I still have it in daily use.
Same for my first MIG, a cheepy 100amp job from '86(?) After doing sterling work for several years, I lucked into my Kemppi. Gave the little job to a local welding shop (migs were not common) and it promply quit. Passed it to my rewinding guy. He sniffed at the ally windings and redid it it with copper. Extremely happy guy. (this is in the context of not much kit being around and high prices for what there was.)

Shenion's comments about house electrics in the USA, didn't they have quite a few house fires from ally cable problems?

The Nat Grid in UK is ally, but with high tensile steel cores to stop the sagging from heat expansion.
KF

Hope this makes sense, I seem to have broken my rule of not posting after three glasses

 

[shenion]

Yes, there were fires from aluminum wiring here. Mainly due to connections corroding.

The main feed from the street and large appliances still use aluminum wire. There are specific torque settings and anti-oxidizing compounds used to do it safely.

 

[madkayaker]

It's very normal for big cabling, switch gear, transformers and the like to be Ali over copper due to cost etc. it's the corrosion that's a problem at point of connection but as said compounds and proper working practices prevent the problems.