Superconducting Cable

21 12 2008

On Dec 4th 2008, I ordered 20 meters of 4mm YBCO superconducting cable from theva. The lead time is 8 weeks, so it hopefully will arrive at the end of January 2009. This should be more than enough cable to complete several basic tests of superconductor construction. I also want to explore the fabrication of a SMES device for high power, high speed lab power supply. We will need to devise circuits to charge and discharge the superconducting cable, I’m not seeing much information on this topic on the internets.  And of course this will require liquid nitrogen. I’ve always wanted to play with liquid nitrogen.

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6 responses

22 12 2008
M. Simon

Charging up a superconducting cable is done this way:

Put the cable in the final form and create a loop. Put a very small heater in a section of the loop that will heat a small section above the transition temperature. Apply your power across this section and slowly ramp up the current. I have read that the ramp up can take as long as 20 minutes.

Once the current reaches the desired level turn off the heater.

You now have your current in the loop. To get the current out of the loop reverse the procedure with a MOSFET as an electronically variable resistor or constant current load.

22 12 2008
M. Simon

BTW you will have to check with your cable mfg about making a superconducting splice.

22 12 2008
ike

heating the cable sounds a lot like the wil-e-coyote school of engineering method. cant you just do it inductively?

22 12 2008
FAMULUS

this is in fact how it’s done:

The short circuit is made by a ‘persistent switch’, a piece of superconductor inside the magnet connected across the winding ends, attached to a small heater. In normal mode, the switch wire is heated above its transition temperature, so it is resistive

http://en.wikipedia.org/wiki/Superconducting_magnet#Persistent_mode

22 12 2008
FAMULUS

We could adapt the repraps heater barrel to form the persistent switch. It would need to be insulated I’d imagine :

http://blog.reprap.org/2006/10/rethinking-mk-ii-heater-nozzle.html

22 12 2008
ike

http://psfcwww2.psfc.mit.edu/ldx/ldx.html#1.1%20Levitated%20Ring

you could make the magnets levitate. elegance, symmetry, and no arcing problems. if you feel like bothering.

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