AC induction motor question - why no motors with aluminum windings and high voltage

[rbrauns]

Hello,

New to the forum. I did do search and found lots of good posts but none the really answer my question so here is my question:

With AC traction induction motors being used more and more for transportation (hybrid cars, trains, etc), why aren't any AC induction motors made with aluminum wiring in the stator? I checked some basic math and if I took a 1000 Watt motor with 14 gage wire and had 10 turns per pole but ran it with 100 Volts and 10 amps, that motor would produce a certain amount of HP and torque. If I assume a 10 foot length of wire for the windings, let's say I substitute aluminum windings but use a smaller gage, say 16 BUT run 5 amps through that motor and use 200 V. Doubling the number of windings per pole but keeping the current half of the lower voltage motor, should produce the same torque assuming I use 20 feet of smaller gage aluminum wire. Is that right so far?

If I calculate the I2R losses using the aluminum wire, I get the same 5.5 Watt loss as the copper wire. That should keep the heat down. Keep the same thought and what happens if I have a 500 volt motor, 2 amp draw and 50 windings per pole? Everything else in the motor stays the same, if possible. The cores may have to get a bit bigger to accomodate the bigger windings. That would make a physically big motor but aluminum is so much lighter and cheaper than copper that someone, somewhere should have produced a motor with aluminum windings by now, so what am I missing?

Sorry if the question is not appropriate but I'm stuck and hope that someone can help me out.

Thanking you all in advance for your help.

Kind Regards,

Robert B.

 

[desertfox]

Hi

Read this it's not quite what your looking for but it might give food for thought

http://www.coppermotor.com/wp-conte...-Induction-Motors-Siemens-Industrial-2000.pdf

 

[Skogsgurra]

I think that the gist of it is in your own words: "The cores may have to get a bit bigger to accomodate the bigger windings. That would make a physically big motor"

But, there's also the problems associated with thin Al wires - they are not easy to use in windings. Reliable termination is one problem.

I also think that wire insulation is another problem. The latter is beacause Al₂O₃ forms on the wire surface and that reduces the insulation laquer's ability to stick to the surface.


Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[waross]

You may apply the same arithmetic to copper windings. At some pint in the design process you must choose a working voltage. Whatever voltage you choose, the motor with the aluminum windings will be larger. That means more iron, and as a result more length of wire. So you are adding costs that may offset some or all of your anticipated savings. Now consider the reduced reliability of the aluminum wound motor. Aluminum does work well and is widely used for the rotor squirrel cage winding.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Compositepro]

I believe the major factor is temperature and strength. An upper use temperature for aluminum is about 400F where it needs to carry any mechanical loads. The wire will melt at a far lower temperature than copper, and there are already plenty of failures caused by copper melting. Corrosion would also be more of a problem, both galvanic and chemical.

 

[rbrauns]

Hi Everyone,

Thanks for the many responses. I kind of figured that there was a good reason why no alu windings are found on motors.

Cheers, RB