13 research outputs found
Thermal Instability and Current-Voltage Scaling in Superconducting Fault Current Limiters
We have developed a computer model for the simulation of resistive
superconducting fault current limiters in three dimensions. The program
calculates the electromagnetic and thermal response of a superconductor to a
time-dependent overload voltage, with different possible cooling conditions for
the surfaces, and locally variable superconducting and thermal properties. We
find that the cryogen boil-off parameters critically influence the stability of
a limiter. The recovery time after a fault increases strongly with thickness.
Above a critical thickness, the temperature is unstable even for a small
applied AC voltage. The maximum voltage and maximum current during a short
fault are correlated by a simple exponential law.Comment: submitted to Superconductor Science and Technology (Dec 2003
Superconducting micro-bearings
This paper presents research into superconducting Micro-Bearings for MEMS systems. Advanced silicon processing techniques developed for the Very Large Scale Integration (VLSI) industry have been exploited in recent years to enable the production of micro-engineered moving mechanical systems. These devices commonly known as Micro-ElectroMechanical Systems (MEMS) have many potential advantages. In many respects the effect of scaling a machine from macro-sized to micro-sized are either neutral or beneficial. However in one important respect the scaling produces a severely detrimental effect. That respect is in the tribology and the subsequent wear on the high speed rotating machines. This leads to very short device lifetimes. This paper presents results obtained from a MEMS motor supported on superconducting bearings. The bearings are self-positioning, relying on, the Meissner effect to provide a levitation force which moves the rotor into position and flux pinning to provide stability thereafter. The rotor is driven by a simple electrostatic type motor in which photo resist is used to pattern the motor poles directly onto the rotor. © 2005 IEEE