Available Technology

BSA 12-18: Radio Frequency-Assisted Fast Superconducting Switch - Recipient of the 2015 R&D 100 Award

An appealing feature of superconducting switching devices is their practically zero conduction loss. This allows a scale-up of the device to very high voltage and current without the penalty of added conduction loss. Switching of electric current through a superconductor is achieved by using the non-linear properties of the superconducting material, which rapidly becomes resistive when any one of the ambient factors, such as temperature, current, or magnetic field exceeds a certain critical value. The most common and reliable way to induce a transition to the normal state is by heating the superconductor. However, thermal activation of a superconducting switch tends to be slow and inefficient at the cryogenic temperatures at which superconducting switches operate. The inventive technology instead induces a current above the critical current to drive the superconductor normal. This technology could enable development of a compact super-conducting switching device suitable for power applications such as a superconducting breaker or a re-closer.
Patent Abstract: 
A novel superconducting fault current limiter (FCL) that relies on the rapid superconducting transition of the material to the normal state. This transition is induced by a radio-frequency (RF) field created by a compact flat coil that is inductively coupled to the superconducting layer. The device can transmit a large amount of electrical energy during the "on" state without additive conduction losses.
This new design retains positive features of the current fault-current limiter (FCL) that do not use external heating to make the transition time very short while minimizing the adverse effect of conductor non-uniformity that is seen in current FCL. This minimization of the adverse effects of conductor non-uniformity could potentially enable the attainment of high off-resistance values.
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