Superconducting wires

Twenty-five kilograms of this experimental superconducting wire can carry as much current as 1800 kg of the bulky cable shown behind the wire. 

For more information about superconducting wires, their metallurgical production and magnet construction see ref. [6, p.187-8],... 

It is clear that the existence of the critical field also implies the existence of a critical transport electrical current in a superconducting wire, i.e., that current Ic, which produces the critical field Hc at the surface of the wire. For example, in a cylindrical wire of radius r, I, = 1rHc. This result is called the Silsbee ntle. 

The copper oxide ceramic superconductors are two-dimensional conductors They can conduct a current parallel to the layers of Cu and O atoms but not between the layers. The fullerides, by contrast, are three-dimensional conductors that conduct equally in all directions. Because of this property, they may prove to be superior materials for making superconducting wires. 

Superconductive wire and systems have seen renewed interest from utilities and government alike after the August 2003-U.S. power outage. Superconductors have the ability to effectively replace overworked portions of the electric grid that contributed to the outage. 

The property of zero resistance is dramatically demonstrated by the phenomenon of persistent currents in superconducting loops. To establish an electrical current in a loop of superconducting wire, the ends of the wire can be connected to a battery in series with a resistor that limits the current, as shown in Figure 2. When switch S2 is closed, the current commences to flow in the loop, and then when switch Si is closed to bypass the battery and S2 is opened to disconnect the battery, the loop resistance drops to zero and the current flow enters the persistent mode. The zero resistance property implies that the current will continue flowing indefinitely. 

For example, American Superconductor (ASC) of Westborough, Massachusetts, in conjunction with Pirelli Cable of Milan, Italy, has produced a prototype, high-temperature superconducting wire that exceeds the current-carrying threshold required for commercial underground power transmission cables. 

At Cambridge s department of physics, Jan Evetts—who has filed at least six patents ranging from the basic physics of ceramic material to designs for superconducting wires— packs ceramic into narrow tubes of silver to create flexible, superconducting wire. Because the silver doesn t oxidize, it allows the oxygen to pass through to the ceramic, which requires it. 

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