[major]

The other question is what type of efficiency gain do you get with the 1 lb gain in weight. Certainly 1 lb is not a good return on $5000. But if you get other gains because of lower resistance, heat dissipation, horsepower gain. $5000 may not be a bad investment. Especially if the part you invest in will have a very long life. How many times can you rebuild an electric motor?

If you keep the mass of silver equal to the mass of the copper, then you will reduce the resistance approximately 5%. Resistive losses account for maybe about 2% of input at rated load. So that equates to a 0.001 (0.1%) increase in motor efficiency or put another way, an improvement in losses of about 1%. So for $5000 (material alone) you make a 88% efficient motor 88.1%.

 

[yarross]

ohms per meter.

Should be Ohm x m.

So for $5000 (material alone) you make a 88% efficient motor 88.1%.

It makes more sense to use copper cage in induction motor instead of aluminium one. This provides about 2% eff gain and costs a lot less.
All this silver hype is an extension to audiovoodoo.

 

[Tesseract]

Should be Ohm x m.

Oh boy - this is the kind of thing that only an engineer can argue about

You are correct that the specification is Ω · m but AFAIK you pronounce the phrase as "ohms per meter". No one I know says "ohms times meters".

In defense of my position, I submit:

http://books.google.com/books?id=IH..._result&ct=result&resnum=6&ved=0CB8Q6AEwBQ#v=onepage&q="ohms per meter"&f=false

It makes more sense to use copper cage in induction motor instead of aluminium one. This provides about 2% eff gain and costs a lot less.
All this silver hype is an extension to audiovoodoo.

I agree times two

However, I *think* the main reasons Al is so popular in this application are it's low density and that it's easy to cast directly into the rotor slots. You can't do that with either Ag or Cu and, of course, both metals are much denser than Al so they would substantially increase the rotational inertia.

But, as usual, major may come along and shoot me down on this

 

[major]

However, I *think* the main reasons Al is so popular in this application are it's low density and that it's easy to cast directly into the rotor slots. You can't do that with either Ag or Cu and, of course, both metals are much denser than Al so they would substantially increase the rotational inertia.

I like the idea of copper cages. A lot of makers use them, but insert drawn bars and weld the shorting rings. Casting aluminum has been a big cost reduction with just a small reduction in efficiency. Recently a lot of work has been done to develop copper casting methods with some good success. I think several makers adopting the method for premium motors. I haven't heard of any progress with casting silver into rotors

 

[yarross]

However, I *think* the main reasons Al is so popular in this application are it's low density and that it's easy to cast directly into the rotor slots. You can't do that with either Ag or Cu

Casting process for Cu presents some challenges - higher copper melting point threatens lamination insulation, and there're problems with high porosity of resulting castings. I've read that pressurized bottom-pour process is the most promising.
There's a dedicated site for die-cast copper cage IMs:
http://www.copper-motor-rotor.org/

and, of course, both metals are much denser than Al so they would substantially increase the rotational inertia.

I don't think that the increased rotor inertia is an issue for EV traction drives.

 

[gor]

...
This may be off topic, but I always wondered what kind of coil performance you could get if you wound a SWNT (singe wall carbon nanotube) in a coild configuration and then passed electricity through it. Carbon nanotubes are ballistic conductors, and can conduct huge amounts of electricity for their size. I haven't been able to find out an answer to this question: Does a conductive carbon nanotube create a magnetic field the same as a metal wire? If you know the answer and have a reference, I would love for you to post.

really interesting - 4 examle, what it could be...?

 

[coulombKid]

History of the project to build the bomb has mention of the use of silver wire. The US government released hundreds of tons of .9999% silver to be drawn into wire for the Manhattan Project. With the good old US-of-A using the lions share of all generated electricity to purify weapons grade uranium the savings really added up. It also freed up the domestic market for copper that was being used over there. While in use on classified projects, the treasury department never really lost control of the silver stockpile. They never even missed it at Fort Knox much the the chagrin of the Japanese. I have steel pennies made during the war years to free up domestic copper for the war effort.

 

[aeroscott]

1% motor eff is 10% less heat , motor builders stuff as much conductor as will fit in the slots . making the motor a little heaver then a copper one with the same size wire . I thought silver was 10% better on size / size . local hot spots silver has it .

 

[coulombKid]

To really do a cost/benefit study one would need to consider things like change of total motor weight, propulsive efficiency of the entire vehicle, and life cycle cost reduction of the battery pack. My gut feeling is that silver is a winner. Using high grade VFD grade insulation and winding support would offset weaker mechanical strength of the wire. The insulators have come a long way in the last century. So has high resistance high silicone steel laminations. In heat transfer classes in E-school we had to calculate optimum insulation thickness for maximum heat transfer. Given the high dia-electric strength insulation available bear in mind thinner is not always better when it comes to heat transfer. A motor with silver windings needs the right type of insulation at the right thickness. Because the current flux density in the stator would be higher, one would need less wire and steel to produce the same Kw rated motor. In the rotor of an AC induction motor silver may or may not be easier to cast than aluminum. It should be much easier to cast that copper and less prone to air bubble inclusions. The high speed/high reliability production tricks to produce silver bar rotors have not been discovered yet so far as I know. When a set of usable Thunder Skys are setting us back 10 Gs I'd think the cost of silver would be a minor consideration. The motors here at work use 200 amps at 4160 volts 3-phase AC. Our annual power usage is so great that we should already have silver windings and silver bar rotors.

 

[malysaad]

Any answer yet?

really interesting - 4 examle, what it could be...?

 

[major]

Any answer yet?

See post #13.

 

[gor]

found something interesting :

http://www.mutr.co.uk/product_info.php?products_id=1009623

Silverthread
conductive thread
[234-315]

in stock £27.94
This is an economical, highly conductive thread for use in hand or machine sewing. This synthetic material feels and behaves like conventional cotton but is made up of over 100 strands each with a nano-coating of silver. It has an electrical resistance of just 4 Ω per 100mm – meaning that just a single thread can be used in place of wires in electrical circuits for LEDs etc. In experiments, we have even run electric motors using up to a metre of Silverthread as a substitute for normal metal wiring. This material can be used in garments and soft products as a woven-in conductor and to secure small circuit boards and wire components to fabrics.

Sold per reel (approx. 50m)

p.s. Bing Search reccommends to check also "kitchen appliances" ... : ((///

 

[aeroscott]

silver conductivity on size basis is 15.8 n ohms / m to coppers 16.78 n ohms / m divided = .94 or 6% better . as stated before motor build to space limits not weight limits .

 

[aeroscott]

is 6% going to be 6% less heat . that's very big for the inner wires that are hardest to cool plus the better thermal conductivity for these inner wires

 

[crap]

Oh boy - this is the kind of thing that only an engineer can argue about

You are correct that the specification is Ω · m but AFAIK you pronounce the phrase as "ohms per meter". No one I know says "ohms times meters".

In defense of my position, I submit:

http://books.google.com/books?id=IHRPAAAAMAAJ&pg=PA117&lpg=PA117&dq=%22ohms+per+meter%22&source=bl&ots=EcATFBx1lf&sig=vQ_8qig-lf0KJAcivpEb0amey5s&hl=en&ei=Ei5SS7L3G-Sdtwe18uz7DA&sa=X&oi=book_result&ct=result&resnum=6&ved=0CB8Q6AEwBQ#v=onepage&q=%22ohms%20per%20meter%22&f=false

.....

Dunno if I wanna be that guy who marks words, but "ohms per meter" is only used for specific wires. For an example, a 1mm^2 wire would have about 0.0172 ohms per meter. However, when talking about a materials resistivity you usually just say "ohm meters".

Now, back to the ongoing discussion in the thread. Silver has about 7,5% lower resistivity, but it has about 17.6% higher density. Properly used, the weight of a motor rewound with silver would increase slightly. The advantage of using silver is the ability to decrease the electrical resistance for a specifik volume, since the volume of conductive material is often limited by the motor design.

This is quite relevant in RC motors, since they have a very high part load and value power density highly. On a high load the conductive losses is the main enemy. Also, cooling is critical due to the high part load. The increased weight of the windings is small compared to the rest of the motor, and since the power can be increased it pays of.

In an electric car however, where the engine is running on a lower part load most of the time, conductive losses may not be the biggest enemy. Iron-losses, bearing losses, and all that is quite likely to be bigger.

My conclusion would be that silver windings in an electric car won't pay for itself in the form of increased range. It mainly pays of in the form of higher power-density.

Of course, there could still be advantages to silver windings that I am not aware of...

Edit: I almost forgot, the resistivity of silver increases less with temperature. Still, that makes the biggest difference at high power outputs, once again the profit in part load efficiency is less.

 

[aeroscott]

thermal conductivity is 429 w/m silver and 401 copper =106.9% , a big cooling aid .

 

[crap]

thermal conductivity is 429 w/m silver and 401 copper =106.9% , a big cooling aid .

Oh yeah, well said. Very useful when trying to increase the motors power.

But once again not very important for part load use, in my opinion...

 

[aeroscott]

a cooler running motor in all conditions will help but how much . stereo guys {some} say silver has advantages at similar frequencies that our controllers use .

 

[gor]

2009 article about copper, silver and Nantennas (antennas)
http://www.thaindian.com/newsportal...tubes-spun-into-threads-open-new-possibilities-in-communications_100167064.html

p.s. not related to copper vs silver:
nanotube wiring: 2009, Nasa, Airforce http://www.xconomy.com/boston/2008/...3/26/nanocomp-wins-air-force-grant-to-make-carbon-nanotube-wiring-for-aircraft/

 

[Haroldesic]

HELLO Unclematt,

My opinion is that, as a human society, we do not care about efficiency. We would rather wear pretty rings and make pretty money than to have truly free energy. If we would replace all copper with silver we could make much more efficient robust generators of all types, wind, water, solar, geothermal.

This would alter the state of our society in a way that would eliminate silver as a material used for jewelry and pretty dishes. As a society we are not willing to give that stuff up.

we would also have to shift the power structure from "those who control oil" to "those who control silver" This would be a costly change - why not just keep it the way it is ???

I also have been looking for a study that shows scientifically, pier reviewed, exactly, what the efficiency increase is for using silver. it sounds to me as if it is much more complicated and more efficient than the 6% TO 9% HIGHER conductivity of silver.
when you consider the lower heat build up will mean a smaller cooling fan, potentially more coils in the same motor, less weight (for car motors). These factors work together putting out higher synergy. resulting in higher efficiency than a simple conductivity comparison.
However; as long as these results are simply "guesswork" and not hard scientific studies we are doomed to do the experiments ourselves. spend tons of money on silver wire and compare our old hand crank generators to the new ones with silver wire. (I plan to do this but it will be a struggle because I am not equipped)
thank you for your post I hope that if you find an answer you will let me know the results and keep in touch with me. Please reply to this post and email direct any reply to this post to oct1113 @ Hotmail.com
I look forward to many replies
Harold