aluminium magnet wire

[charlie_r]

I took apart a broken clothes dryer, and disassembled the motor from it.

After unwinding all the wire from the motor, I cleaned off some of the enamel, in preparation for winding a few coils for a project I'm working on. I got one heck of a surprise! It's aluminium! (yes I know I'm using the british spelling)

Has anyone else ever seen this?

When did the motor manufacturers start doing this?

 

[Sceadwian]

How did you determine is was aluminum? How old is that clothes dryer? Aluminum wire used to be common, a long time ago though.

 

[charlie_r]

It appears to be aluminum. Very soft white metal, and will not take solder. Easily bent, and breaks with not much tension.

The dryer it came out of was about 20 years old. Actually replaced the motor in a similar dryer, and it appears to have the same motor in it too. Will unwind that motor as well, even though I can see the shorted windings in it.

 

[Sceadwian]

Aluminum wire used to be pretty common in motor and household wiring. Don't know what the cutoff is, but 20 years seems a little new to to have it, but not unusual per say. I'm not sure the reasons behind it exactly but that's the way it was. Many old houses still have aluminum mains wiring, but again, 20 years seems a bit new for that.

 

[cobra1]

its a bit longwinded but i belive that aluminium wire was used in the 70s, it was stopped due to the fact that aluminium expands and contracts and in doing so can corrode, by corroding it causes the resistance to climb and therefore the aluminium wire gets hot and can cause fires.

this may have also been the case for motors too

 

[charlie_r]

I am very much aware of the issues of aluminum residential wiring, having replaced what seems like 1 million miles of the crap over the years as an electrician. This is why I am fairly certain that the wire I pulled from the motor is aluminum, abt 16ga on one set of windings, and abt 20ga for the other. Rather large for a 1/4 hp dryer motor. If it had been copper, it probably would be several sizes smaller.

 

[Sceadwian]

I still don't understand the reasoning for using aluminum in a motor though, the coil is going to be bigger and provide not advantage.

While cobra's reason for the discontinuances of aluminum wire is technically right it's not the wires fault per say, but the connection itself. Aluminum wire really need to be pierced and clamped/crimped.

 

[charlie_r]

About the only reason I can figure that the motor manufacturers would use aluminum would be cost. Having replaced one of the motors, I can tell you that the new motor is identical to the old. I just had never come across this before, that is why I asked if anyone else had.

Now, the real question is, will coils made from this wire need to be wound different for my project? What I am attempting to build is a type of pulse generator, for a set of flashing lights, the pulse rate to be determined by ground speed on my bicycle.

 

[Warpspeed]

Aluminium windings are used in all sorts of things, copper costs around thee times as much (by weight) as aluminium.

Sure it has greater electrical resistance, but if you are manufacturing something, you design it to use aluminium wire and save heaps.

 

[Andrew Leigh]

Hi,

I make aluminium wire which is used primarily in large distribution transformers. There is a crossover point at which aluminium becomes cheaper than copper, it is at this point that manufacturers change designs. For the producer it is a pain as it take 3X the resources for an equivalent kg of copper, this ties up capacity.

Cheers
Andrew

 

[fernando_g]

About two or three years ago, when the world's market price for copper was skyrocketing, I actually saw a cheap UPS whose transformer was wound with aluminum wire.
The failure was precisely what other poster mentioned: the end of the aluminum wires, which had been crimped to a spade connector, had corroded and become intermittent.

 

[giftiger_wunsch]

About the only reason I can figure that the motor manufacturers would use aluminum would be cost. Having replaced one of the motors, I can tell you that the new motor is identical to the old. I just had never come across this before, that is why I asked if anyone else had.

Now, the real question is, will coils made from this wire need to be wound different for my project? What I am attempting to build is a type of pulse generator, for a set of flashing lights, the pulse rate to be determined by ground speed on my bicycle.

The only difference between aluminium and copper wire should be resistance and reliability (aluminium is one of the more reactive transition metals and as such is easily corroded as already mentioned).

 

[Warpspeed]

As above, aluminium has higher electrical resistance, so you will need to go up in wire gauge, otherwise electrically, it will work exactly the same.

The problem is terminating the ends, because normal tin/lead solder does not work with aluminium.
Screw terminal blocks are probably the best, but not really practical for very small transformers.

Unless you are into serious mass production, or have a definite reason to use aluminium wire, stay with copper wire.

 

[Nigel Goodwin]

I can't say I've ever seen aluminium wire used anywhere? - although I'm told it's used for the HV power lines?.

Certainly it's never been used for mains wiring here, what a horrible idea!.

I thought two copper wires with flax insulation, covered by a lead sheathing, was bad - but not as bad as aluminium.

 

[Warpspeed]

Aluminium windings have been around for quite some time, particularly in the lower cost brands of small arc welders commonly owned by hobbyists.

 

[giftiger_wunsch]

Certainly it's never been used for mains wiring here, what a horrible idea!.

Sounds like it'll be used with battery-voltage on this project, so no real problem there. Aluminium should be fine as long as the OP accounts for the higher resistance and realises that it may be more prone to damage than copper wire would be.

 

[giftiger_wunsch]

Aluminium windings have been around for quite some time, particularly in the lower cost brands of small arc welders commonly owned by hobbyists.

Personally I would just stick with copper. It may be more expensive when considering mass-production, but low reactivity and high electrical conductivity are the two main reasons why it's used, and aluminium is second-rate in both areas.

 

[Warpspeed]

Personally I would just stick with copper. It may be more expensive when considering mass-production, but low reactivity and high electrical conductivity are the two main reasons why it's used, and aluminium is second-rate in both areas.

Very true.
In fact I have replaced burned out aluminium windings with copper, simply because the copper wire is more readily available.

 

[Sceadwian]

Certainly it's never been used as mains wiring?
Nigel, it was commonplace up until the 70's for new homes to be built with aluminum wiring, at least in the states, if you buy a home in many older neighboorhoods you'll still have to deal with it. It's not that horrible of an idea, aluminum oxidizes into a self insulating corrosion product. Expansion and contraction with heat makes connections an issue, but if enough of it is used it's cheaper than copper and just as reliable when done by someone that knows what they're doing.
As I said in a previous post the primary issues is contact problems, and it's relatively easily solved by using piercing connections. Aluminum is far more ductile than copper and if the connection is solid it's just as good, if not slightly larger than a copper wire, and with a slightly lower ampacity due to the over all thermal load. It's basically an issue of cost. Personally I'd just use copper, I know it's electrically conductionwise better, and I think it's thermally conductivity is better as well.

 

[giftiger_wunsch]

aluminum oxidizes into a self insulating corrosion product

While aluminium does rapidly build up a layer of oxidation, that doesn't protect it definitely. It's still a great deal more reactive than copper, and less reliable for that reason. Combined with the other problems mentioned, it's really just the cheap and nasty way to do the job.