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Materials used in electric motors, coils etc in F1 cars


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#1 Alexandros

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Posted 10 June 2014 - 23:13

Is there any rule prohibiting the use of silver wire (better conductivity / inductance than copper) in things like energy recovery systems, electric motors, alternators etc?

 

If not, is silver being used instead of copper?



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#2 HaydenFan

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Posted 10 June 2014 - 23:25

http://www.formula1....s/8699/fia.html



#3 gruntguru

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Posted 10 June 2014 - 23:43

No mention of silver in the regs. It would certainly make sense to use it in critical areas.



#4 peteringram

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Posted 11 June 2014 - 07:48

I think silver is good for very small motor. it also transfers heat better.



#5 Alexandros

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Posted 11 June 2014 - 08:34

I think silver is good for very small motor. it also transfers heat better.

 

Yeah I've seen some remote controlled planes use silver coils in their (tiny) electric motors... but in theory it's the same really whether small or large. There's also the option of silver plated copper wire but IIRC this is better for high frequency applications.

 

It's probably used more in small applications due to the cost of silver. A hybrid car using 5-10kg of silver wires might have a "premium" on it for something like +10% extra range / +10% performance (it would pay back eventually and the silver is not lost - it can be scrapped), however given that finding tenths in a f1 car takes millions of USD, the cost of silver is nothing (~600 USD per kg) in comparison. And in this case too, it's not a cost wasted. It remains as an asset if the team wants to recycle old components.



#6 Joe Bosworth

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Posted 11 June 2014 - 09:22

I am not into the details of designing either electric motors or generators.  But I do realise that they work on the principle of utilising the electrical flux resulting from the flow od the ions.

 

For an optimised design as might be applied to F1 concern is likely to be either getting the best curent flow per unit volume or flow per unit weight.  It is hard to understand which characteristic is most important,volume or weight.

 

But under any circumstances lets compare copper as a conductor versus silver and aluminium. The following shows the conductivity and density for the three metals.  Conductivity units are in siemens per meter, (the higher the value the better the conductivity) and density in grams per cubic cm, (obviously the lower the better).  The data is provided is mid range for each as there is some small variation due to alloys being used.

 

Silver has a conductivity of 6.2 and a density of 10.5     Ratio of conductivity to density is .59

Copper's conductivity is     5.95 and density of    8.98   Ratio of conductivity to density is .66

Aluminium' conductivity is  3.5 with density of      2.7     Ratio of conductivity to density is 1.30

 

Thus silver flows electricity 4% better than copper but weighs 17% more.  Silver's savings in space is small but the weight penalty is pretty high. Aluminium flows electricity  at only 58% of copper but weighs only 30% of copper.  If space is paramount aluminium wouldn't be used but it is more than twice as effective than either silver or copper on a weight basis for the same elecrical flow.

 

Regards



#7 MatsNorway

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Posted 11 June 2014 - 20:51

One thing that allows higher efficiency on at least RC cars and i believe it also to industrial 3 fase motors is that with more polar pairs (right word?) you get lower rpm and higher efficiency.

 

Other variables to play with is for instance to sacrifice efficiency by going under size motors. As electric motors does not really have a static power output as that in turn is all down to how much you stuff into it.

 

Given that it is a weight limit to the power unit and i assume it includes the motors too weight might not be that big a issue. 130kg now. But since there allready is a decent amount of empty space between hot and cold side on turbo you can focus on weight and efficiency.

 

(blabla incorrect stuff removed)

 

Last comment is that i think its certain that it is most likely copper in the Turbo KERS unit.

 

And aluminium is out regardless i think.

 

http://www.lrp.cc/en...ed-40t/details/


Edited by MatsNorway, 12 June 2014 - 10:02.


#8 Alexandros

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Posted 12 June 2014 - 07:06

 

Last comment is that i think its certain that it is most likely copper in the Turbo KERS unit.

 

 

So there is room for improvement in your opinion?



#9 MatsNorway

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Posted 12 June 2014 - 10:01

Today im not sure why i answered that. ¯\_(ツ)_/¯

 

You can scratch all i posted about the weight. The total weight was perhaps 20-25kg on the old systems...

 

Source:http://www.racecar-e...kers-batteries/

 

but  the motor alone was 5kg

Source: http://www.magnetima...xcellences/kers

 

efficiency at 95-97% at 100degrees. (pretty damn good)

 

Being able to get rid of heat is another big factor, have a look at this:

table_2_5_1.gif

 

 

 

Yea silver sounds reasonable now. Probably as much as possible unless denied through a materials list you have not found.

 

Eddie Currents

One thing that i did not mention yesterday is that eddie currents goes higher at higher rpm (due to higher frequency) http://en.wikipedia....ki/Eddy_current

Thats why you go up in poles and down in rpm and gain efficiency.. So the KERS and the Turbo KERS is probably very different. one needs to go up to 100krpm and the other one could be geared down to whatever best suitable. unless rules again.. one set of spur gears got a efficiency at about 99% so you might have some wiggle room in the design. If it is at 95% mounted on the crank with todays rpm, but has higher potential if lowered in rpm. I have no clue about how big an effect the eddie currents has only that it is there.

 

I think the biggest los is in the magnetic fields due to clearances between the stator and rotor. Eddie being a smaller part of it.

 

On the mercedes link above they have it directly on the crank. so up to 15000rpm if they still do it like that. With a planetary gear it could have been mounted lower without much space wasted. It also sounds like better packaging. Unless fuel tank is there. Then it wont matter as much as if the battery is there and gets a odd shape.

 

Main benefits of having a low rpm motor is that it got tons of umpf from low rpm. Thats handy in the start. Efficiency and torque is much more stable across the board too. That said the extra weight from the gears can be added to the motor to make it bigger so i doubt they do it.


Edited by MatsNorway, 12 June 2014 - 10:30.


#10 Kelpiecross

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Posted 12 June 2014 - 11:44

I have heard of silver being used to make a whole two-stroke head - Ag having the greatest heat conductivity of any metal.
Ag is not fiendishly expensive at about $22 per ounce - the F1 teams have such enormous budgets that you would think they would not worry about the cost and would use Ag if it was better.

#11 Alexandros

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Posted 12 June 2014 - 16:44

I have heard of silver being used to make a whole two-stroke head - Ag having the greatest heat conductivity of any metal.
Ag is not fiendishly expensive at about $22 per ounce - the F1 teams have such enormous budgets that you would think they would not worry about the cost and would use Ag if it was better.

 

It is better, there is no argument about it. It is more thermally conductive, more electrically conductive and has higher inductance at the expense of extra weight. But we are talking about wire, so... it's not like wire weighs >10kg.

 

Another solution is top-quality copper wire. There are some copper wires that exceed normal copper wire specification by 1-3%. They are usually much purer (>99.9%) and created at an air-vacuum or something to eliminate tiny bubbles.

 

Silver plating can also be an option (current traveling faster at the periphery of the wire than the core).

 

Or... there could be a custom order of silver core and copper periphery (not plated). So it's like a wire within a wire with the faster conductor being at the center.



#12 ray b

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Posted 12 June 2014 - 19:22

we used silver wire in racing slot cars in the late 60's

that cost far more but was a bit faster

 

I wonder in alloys have been tested to see if any mix is better then pure metals

 

I do know the high temp[over near  0 k] low resistance trys used some very exotic metal alloys  to get to Superconductivity like YBa2Cu3O7,

and wonder if other alloys would work at normal temps better then pure copper or silver



#13 Alexandros

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Posted 13 June 2014 - 05:18

Alloys of copper and silver usually suck in terms of resistance / conductivity. As pure as it gets is the way to go.

 

(I'm not familiar with superconductor alloys)


Edited by Alexandros, 13 June 2014 - 05:25.


#14 Canuck

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Posted 14 June 2014 - 04:30

With respect to copper coating a silver wire - it seems to me that electricity has a preference for running on the OD, or primarily on the OD.  Skin Effect maybe?  At any rate, I think the Ag coated Cu would be more effective of the two, and cheaper than pure Ag wire.

 

Edit - applies to AC only. 


Edited by Canuck, 14 June 2014 - 04:33.


#15 ray b

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Posted 25 June 2014 - 17:49

hijack but related

 

why doNOT car starter motors use capacitors ?

like A/C motors do



#16 bigleagueslider

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Posted 26 June 2014 - 02:45

Is the weight/performance benefit provided by using silver wire in the motor/generator stator windings worth the added costs? Copper conductors in PM motor/generator stator windings work very well overall. Are the copper stator windings actually the limiting factor with the PM motor/generators used in F1? Or are the capabilities of the PM materials more of a limiting factor?

 

How about saving weight by using aluminum conductors for the vehicle wiring system?



#17 gruntguru

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Posted 26 June 2014 - 03:23

As mentioned earlier in the thread, the added costs would be small by F1 standards, so if there is any performance benefit it would be done.



#18 Kelpiecross

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Posted 26 June 2014 - 06:43


Maybe Ag doesn't make a good wire in a mechanical sense?

#19 MatsNorway

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Posted 26 June 2014 - 14:00

Its not as elastic as copper

http://www.copper.or...operties/144_8/

 

Copper pure was stated in a book here to be 60%

 

Aluminum seems to be at its softest to be about 35%

http://www.alueurope...ctures/1501.pdf

 

Silver seems to be at about 30% or less if hardened.

http://www.doduco.ne..._24-10-2011.pdf

 

But i doubt its an actuall issue given the lack of rules on the shape of the turns and windings in the stator. You can engineer your way out of it IF it becomes a issue. Flat wiring in the bends and such.

 

I think Eddie Currents is a bigger challenge for them once they go low on turns to get more power.


Edited by MatsNorway, 26 June 2014 - 15:46.


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#20 Alexandros

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Posted 28 June 2014 - 10:11

As mentioned earlier in the thread, the added costs would be small by F1 standards, so if there is any performance benefit it would be done.

 

Not every team is using optimal solutions - that's a given... some find performance benefits in various areas and exploit these benefits and some others ...don't. Otherwise they'd all have the exact same performance. There are simple things that teams often overlook. Take for example the air composition to fill the tires (Stepneygate). You'd think this is something that a top team like Mclaren would already have experimented on their own - but apparently they hadn't.



#21 Alexandros

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Posted 28 June 2014 - 10:16

Its not as elastic as copper

http://www.copper.or...operties/144_8/

 

 

 

It can be used as wire / coils, so - no problem there. In fact, during WW2 (Manhattan project) they used tons of silver for this purpose.

 

http://phys.org/news182628141.html



#22 MatsNorway

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Posted 28 June 2014 - 12:13

Dont make it sound like i claimed one can not make wires out of it.



#23 Greg Locock

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Posted 29 June 2014 - 02:12

Hardening a pure metal will tend to reduce its conductivity. The effect may not be huge, but it is inevitable.



#24 Joe Bosworth

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Posted 29 June 2014 - 11:17

Greg

 

Per your input above, "Hardening a pure metal will tend to reduce its conductivity. The effect may not be huge, but it is inevitable":

 

I find this intersting and have never come across this before.  Would like to understand the details as to why this is so.

 

Can you provide a source thaty I can track down as to why.

 

I have always understood that metal haardness was related to the shape and size of the crystal structure and that electrical current is ion flow which is sub molecule and sub crystal structure.

 

Regards



#25 Greg Locock

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Posted 29 June 2014 - 11:51

As you work harden a metal you create and move the grain boundaries, which provide some of the resistance to motion of the electrons. As you add alloys to a metal it upsets the crystalline layout of the atoms, so again impeding the flow of electricity.

 

http://www.newton.de...5/mats05186.htm

 

http://www.afsinc.or...ItemNumber=7810



#26 bigleagueslider

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Posted 02 July 2014 - 05:53

It's not just the properties of the stator windings that are of concern. There is also the properties of the stator laminates to consider. There are the properties of the PM materials to consider. There are the capabilities of the power electronics devices to consider. The PM materials (like neodymium) have definite operating temperature limits, and it is quite difficult to cool the PMs on a high-speed rotor.



#27 MatsNorway

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Posted 02 July 2014 - 09:08

http://en.wikipedia....etic_properties

 

They have a limit usually at 310 degrees it says. Cobalt magnets can take higher temps but they are weaker. Neo it is.

 

Cooling the rotor was at least done with a hollow shaft with cooling going through last time i found an article on it. Cooling requirement total is about 2.4kw. if they are up on 97% 



#28 bigleagueslider

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Posted 04 July 2014 - 05:29

The neodymium materials used on high-speed PM motor/generator rotors have a practical temp limit of around 250degC in typical service. But it's also difficult to adequately cool the material when it is adhesively bonded to the outside of a steel rotor shaft. The conductive heat tranfer path from the outer magnet surface and thru the magnet thickness, across the adhesive bond line, and thru the thickness of the rotor shaft, is not very efficient. Plus the cooling fluid is typically something like180degF lube oil. Neodymium PM materials also have limited mechanical strength. So when used on a motor/generator rotor turning at speeds well in excess of 20Krpm, the magnets must have some sort of retaining sleeve installed over them to prevent them from coming apart due to high CF forces.



#29 gruntguru

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Posted 04 July 2014 - 08:19

"The rotational speed of the MGU-H may not exceed 125,000rpm." 

 

Yes - well in excess of 20k!