BassAwdyO said:
Um, it's what I do for a living..
Here's a link to the stuff on the HTS wire..
http://www.amsuper.com/products/htsWire/103419093341.cfm
Typically, the wire vendors will not provide much in the way of detail when it comes to using their product. For complete cable solutions as an example, they will sell you a full 3 phase tenth of a million volt 20 or 30 kiloampere wire run, but won't teach you how to make one using their product. The construction tidbits I gave are just from experience..
Designing a superconducting speaker is quite trivial, as typical applications I deal with run 10 to 15 KPSI lorentz forces...the biggest problems will be mag field safety,ODH issues, and frostbite.. That, and the liquid useage will be very high for such a small power application as to be useless..even at 32 cents a quart, it'll take a lot of LN2 to keep it cold. Overall, a superconducting speaker can be very difficult, and can be dangerous ta boot..
Cheers, John
To keep the design reasonable, you have to separate the motor from the cone. If you use a tubular connection rod made of kevlar or composite graphite, you can have the motor as a seperate entity.
To insulate the cryo sections, you'll need to either maintain a thermal gradient with nitrogen boiloff, or use a vacuum..
A vacuum is a problem for the connection rod..motional seals will have to be very flexible, and you need two, one on each end, to eliminate the 15 psi resulting. If you assume an xmax of an inch or two (hey, might as well make use of the materials), that makes the seals an issue for vacuum..normal seals are stainless bellows, they'd fatigue way too fast..
If you use the nitrogen boiloff, the seals could be simple thick felt sliders...you could try o-rings, but they'd have to be something that remains flexible down near 77K. The coupling rod will conduct heat inward, so you'd be fighting the ice ball at the seals. A thin styrofoam insulating layer over the rods would help. On the inside of the cryo system, graphite axial fins would help keep the rod cool near the supers..I'd go with designing the rod with taper and incorporate the vc in the structure..you can buy graphite unidirectional weaves online...I'd use west system's epoxy with the tropical hardener for pot life..
Connections off the rod would have to be normal material, as the hts will not survive the flexure. Bond the hts to the rods soldered to copper flat stock for at least 2 inches overlap...then, copper litz off the rod to the stationary connection. One on each side of the active voice coil, that way, you do not have to worry about the layer transition area required for a two layer vc with leads out one end.
The field coil is trivial in comparison.
Cheers, John
To insulate the cryo sections, you'll need to either maintain a thermal gradient with nitrogen boiloff, or use a vacuum..
A vacuum is a problem for the connection rod..motional seals will have to be very flexible, and you need two, one on each end, to eliminate the 15 psi resulting. If you assume an xmax of an inch or two (hey, might as well make use of the materials), that makes the seals an issue for vacuum..normal seals are stainless bellows, they'd fatigue way too fast..
If you use the nitrogen boiloff, the seals could be simple thick felt sliders...you could try o-rings, but they'd have to be something that remains flexible down near 77K. The coupling rod will conduct heat inward, so you'd be fighting the ice ball at the seals. A thin styrofoam insulating layer over the rods would help. On the inside of the cryo system, graphite axial fins would help keep the rod cool near the supers..I'd go with designing the rod with taper and incorporate the vc in the structure..you can buy graphite unidirectional weaves online...I'd use west system's epoxy with the tropical hardener for pot life..
Connections off the rod would have to be normal material, as the hts will not survive the flexure. Bond the hts to the rods soldered to copper flat stock for at least 2 inches overlap...then, copper litz off the rod to the stationary connection. One on each side of the active voice coil, that way, you do not have to worry about the layer transition area required for a two layer vc with leads out one end.
The field coil is trivial in comparison.
Cheers, John
well the ultimate superconducting speaker would have a superconducting voicecoil and a superconducting magnet and maybe some feedback loops in there too but if we cant really do that, then might as well just do a low inductanc feild coil superconductor with a long high inductance voice coil which would be fed a constant voltage. the superconductive feild coil could do all the changing... any problems with that?
BassAwdyO said:
Um, yah...sorry...
Eddy currents within a conductor are dependent on the rate of change of the magnetic field trying to go through.
A superconducting voice coil will force the magnetic circuit to change it's total flux, and the gap field will be perpendicular to the voicecoil winds..meaning, as you increase power or frequency of the drive signal, you will start to heat the HTS tape. Start to leave the gap, and poof, you're up about 100 degrees.
AT 77K, all materials have reduced heat capacity...Helium is the lone exception. Copper vc would work also, as at 77K, it's heat capacity is .17 Joules/gram-K, vs room value of .38...half.
And, it's resistivity is about .1 e-8 ohm meter at 77K vs room value of 1.7. You pick up a 17 to 1 advantage just by cooling it..
Cheers, John
a lot of this is out of my knowldge an a lot i can also understand...but damn im only in HS 
But from my understanding i think that pulling this off will be a VERY large task.
and that is just to get one fo actually play some sort of tone. getting one to work like todays drivers work...well its going to take years and years of development. you may get one right by the time you are too old to care.
Someone suggested a lump of superconductor in place of a magnetic feild. however you are having to buy 200 meters of superconducting wire.
an idea. put a coil inside a coil. with opposite polarities. wire them in parallel out of phase so they will be repeling then atracting each other. i have no idea if this would actually work or not but its an idea i am thowing out.
another idea is to have a driver that works 1 way. indstead of the back and forth movement. Because superconductors repel magnetic feilds you could have the coil inside a coil idea, and only play half the sinewave and the other coil un powered. then rely on the suspension for the back stroke.
one problem that you will have is the suspension. you will need some sore of suspension. your conventional spider will get far too brittle at 180K. you could use copper coil springs like on adires parthenon.
But from my understanding i think that pulling this off will be a VERY large task.
and that is just to get one fo actually play some sort of tone. getting one to work like todays drivers work...well its going to take years and years of development. you may get one right by the time you are too old to care.Someone suggested a lump of superconductor in place of a magnetic feild. however you are having to buy 200 meters of superconducting wire.
an idea. put a coil inside a coil. with opposite polarities. wire them in parallel out of phase so they will be repeling then atracting each other. i have no idea if this would actually work or not but its an idea i am thowing out.
another idea is to have a driver that works 1 way. indstead of the back and forth movement. Because superconductors repel magnetic feilds you could have the coil inside a coil idea, and only play half the sinewave and the other coil un powered. then rely on the suspension for the back stroke.
one problem that you will have is the suspension. you will need some sore of suspension. your conventional spider will get far too brittle at 180K. you could use copper coil springs like on adires parthenon.
BassAwdyO said:
in this direction -
http://www.acoust.rise.waseda.ac.jp/~mas-oka/ICA2004_yamasaki.pdf
at last ...
( with thanks to lrntglls )
7548
I am not professing to be a particle physicist, so I am not going to go into equations, but I think you have misunderstood the nature and usefulness of the meissner effect.
The superconductor's crystal lattice becomes impermeable to magnetic fields, so there is not resistance *because* the energy is not taking the form of electrical energy travelling through the crystal lattice, it is taking the form of electromagnetic energy passing along the skin of the material. If you are looking to create a magnetic field, this is not a problem. If you want the magnetic field to go the other way, load it up with an opposite current.
Since it is a surface behaviour, almost like total internal reflection, where the energy is not actually penetrating the material but interacting with it at a a boundary, there will probably be some counter-intuitively high performance nanotechnology surface treatments in the future which will allow current conservative engineering estimates of the highest possible superconducting temperature to be substantially surpassed.
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I would suggest that the most sensible design for a superconducting motor for an electro-acoustic transducer would be to employ a superconducting field coil, which would likely substantially cool a voice coil assembly to the point where the voice coil assembly would be able to tolerate much higher currents without self-immolating or producing a change in resistance value due to heating and exhibiting power compression.
Would be interested to see any mathematical estimates of exactly how much power one would be able to fit into an actively cooled superconducting field coil loudspeaker.
A speaker is just a type of electric motor, people are already experimenting with superconducting solenoids and cooled stators in industrial high power motors.
Superconducting motor to increase power density
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