Comments on: Superconducting Cable

By: ike

ike — Mon, 22 Dec 2008 02:11:53 +0000

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.

By: FAMULUS

FAMULUS — Mon, 22 Dec 2008 01:49:19 +0000

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

By: FAMULUS

FAMULUS — Mon, 22 Dec 2008 01:46:43 +0000

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

By: ike

ike — Mon, 22 Dec 2008 01:43:26 +0000

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

By: M. Simon

M. Simon — Mon, 22 Dec 2008 01:02:35 +0000

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

By: M. Simon

M. Simon — Mon, 22 Dec 2008 00:50:49 +0000

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.