Aluminum Windings vs. Copper Windings

Yes, TVP45 is correct also Aluminium is more rigid than copper so making windings would be more difficult

Well I bought a arc welder with aluminium windings about 30 years ago- hasn't faulted. At the time, was the only welder with 5 year warranty. THIS IS OF COURSE subject to duty cycle- this machine was only one with 25% duty cycle. Over the years it has welded all that I required very well- from 20G TO 3/8" steel. And using carbon arc torch has enabled brazing also. from my understanding of the subject, it is overloading of duty cycle that overheats windings, whether copper or alum- which causes insulation between winding breakdown resulting in shorted turns.

Hello Neil Kwyrer

Your electric welder is not a large one, as your maximum work appears to have been ³/₈ inch steel.

Almost certainly the primary winding is copper, with the secondary being aluminium flat insulated strip.

Perhaps you live in a location where that welder experiences no high humidity.

A welder in which the aluminium winding (even the strip type) has survived 30+ years is perhaps the exception, or you are in a very low humidity area.

Kind Regards....

GA Sparky, GA....

Welders are certainly not typical transformers. They are designed to have relatively high impedances to limit the current in the arc. This not the case for typical transformers...

In the US, nearly all utility distribution transformers have aluminum windings submerged in oil. The oil protects the windings from corrosion, and provides greater heat removal capacity than air.

The main disadvantage for utility use is the higher I²R loss in aluminum windings. Every watthour lost is one more which must be generated, but can't be sold for revenue. Regardless of the winding material, the cost analysis for purchasing a transformer should consider not only the capital cost of the equipment, but also the cost of the losses over the expected life of the transformer.

For commercial and industrial customers, copper windings are more common. In units above 2500 kva, the losses are often high enough to offset the lower initial cost of aluminum windings, making copper a better deal.

Hi,

this situation is not as easy as it may look like:

Lower density (factor 3) is only partially compensated by higher resistance (factor 1.5).

So if the space is available to allow a winding cross section of 1.5 ...2 times a comparable copper winding there is the same resistance and still a gain in density of 2 ... 1.5.

Lower heat conductance (200 compared to 400W/K.m) of Al may require better cooling if the same insulation system is used.

Copper has to be insulated by PU or EP plastics depending on maximum temperature.

These plastics have thermal conductivities below 0.1W/K.m

Aluminum may be insulated by anodising.This has a thermal conductivity above 15W/m.K and is made much thinner as the breakdown voltage is very high.

And any known bad experience with corrosion of aluminum is gone if anodised wire is used. This is a special ductile anodising treatment that survives well the bending at winding. Also high quality polymer coating will be good for aluminum.

Windings have a lengthwise thermal resistance that is given by the fill factor but crosswise the thermal conductivity is given by a serious connection of many metallic with many insulating layers.

So in total the aluminum winding is better with respect to weight and acceleration.

(At constant resistance).

And aluminum may also be better if the same cross section is used, if the higher heat is distributed easily by anodised aluminum wire.

So any application that requires 1. minimum weight: airborne, space,

any application that requires 2. maximum acceleration: hard disc drives, servo-motors,

and any application where 3. cost is to be considered: high volume applications,

all these will be future candidates for aluminum - some realisations are existing today.

(There have been transformers with aluminum windings used in aircraft as early as 1940).

RHABE

>> Apart from cost are there any other advantages (or disadvantages!)
>> of using aluminium instead of copper wire for winding transformers

Assuming you are talking substation or distribution power transformer's, as used by your local electric company; there are no significant differences in these two choices.

Utilities rarely include winding material constraints in their transformer specifications; rather the will specify a economic formula for the evaluation of transformers bid by the manufacturers, for example consider the following simple evaluation formula:

EvalPrice = Purchase_Cost + ( No_Load_Losses * $NL/W ) + ( Load_Losses * $LL/W )

Where:

• Purchase_Cost - is the bid cost from the manufacturer
• No_Load_Losses - is the manufacturer's design no load losses (in watts)
• Load_Losses - is the manufacturer's design load losses (in watts)
• $NL/W - is the utilities evaluation costs for each watt of no load losses added to the system
• $LL/W - is the utilities evaluation costs for each watt of load losses added to the system

The manufacturer's have very good systems in place for designing and manufacturing transformers with either copper or aluminum windings.

Since posting, I have checked white papers from a number of transformer manufacturers. I believe that generally companies that use aluminum state that aluminum is superior and give reasons why, and companies that use copper state that copper is superior and give reasons why. I suspect that I am probably biased toward copper since that is what I've used and that aluminum may indeed be as good (or even better?). It's the old case of "when you're a hammer, everything looks like a nail".

Hello TVP45

You did it !

Kind Regards....

can someone give me a mathematical proof as to why the aluminium winding cross sectional area is larger than that of the copper winding....and how much...

thanks...