Wisconsin Alumni Research Foundation

Xianrui Huang

Yehia M Eyssa

Roger W Boom

Mostafa K Abdelsalam

Mostafa M Abdelsalam

A compressive strut for cryogenic applications includes a tube with a cylindrical bore wall defining an internal cavity, a rod of filling material within the cavity which has low thermal conductivity, and structure in engagement with the rod, such as end plugs partially inserted into the ends of the tube and in contact with the rod. The tube may be formed of a composite material such as fiberglass within a matrix of epoxy, wherein the fiberglass fibers are wound circumferentially. The plug at one end of the strut is attached to the warm support structure and the plug at the other end is attached to the cold structure, such as a superconducting magnet which is maintained at cryogenic temperatures. Compressive pressure applied by the magnet to the strut causes the plugs to press inwardly on the filling material rod, expanding the rod radially. The circumferentially strong tube resists outward expansion of the rod and carries a significant portion of the compressive pressure applied to the rod so that the rod itself does not have to support the compressive forces applied to it. Consequently, the rod can be formed of a relatively low thermal conductivity material which need not have high strength, and the tube need only have high strength in the circumferential direction.

Compressive strut for cryogenic applications

A thermal plug which provides an electrical connection between first and second regions at different temperatures includes a plurality of interleaved heat transfer resistive laminae and heat conductive laminae. The laminae are stacked together to form a laminate and a plurality of superconducting strands are attached to the stack such that they are in thermal contact with the laminate. The superconducting strands are also in electrical contact with a conductor (e.g., a low temperature superconductor), in the first region and a conductor in the second region to allow the supply and withdrawal of electrical energy to and from the conductor in the first region.

Superconducting connecting leads having thermal plug

A superconducting energy storage magnet is constructed for mounting in relatively shallow trenches or tunnels to provide superconductive energy storage for applications such as power system load leveling. The magnet includes composite superconductors arranged in substantially planar coil layers around a central axis. A first and second coil layer have an inner support structure between them to which the conductors of the layers are engaged. The inner support structure carries the magnetically induced forces on the conductors of the coils. The net radial magnetically induced force is opposed by the rigid structural material of the inner support structure and by support struts which extend from the periphery of the inner support structure to a surrounding support wall such as the wall of a trench. The conductors in each layer, and the inner support structure between them, have matching vertically (axially) undulating ripples over the circumference of the magnet. The ripples accommodate stresses imposed on the magnet during cool down from ambient temperatures to cryogenic temperatures, while the inner support structure is rigid radially to carry the magnetically induced radial forces on the conductors so that substantially no flexing of the conductors occurs during charge up and discharge of the magnet.

Vertically rippled superconductive magnetic energy storage

A superconducting magnet is formed having composite conductors arrayed in coils having turns which lie on a surface defining substantially a frustum of a cone. The conical angle with respect to the central axis is preferably selected such that the magnetic pressure on the coil at the widest portion of the cone is substantially zero. The magnet structure is adapted for use as an energy storage magnet mounted in an earthen trench or tunnel where the strength the surrounding soil is lower at the top of the trench or tunnel than at the bottom. The composite conductor may be formed having a ripple shape to minimize stresses during charge up and discharge and has a shape for each ripple selected such that the conductor undergoes a minimum amount of bending during the charge and discharge cycle. By minimizing bending, the working of the normal conductor in the composite conductor is minimized, thereby reducing the increase in resistance of the normal conductor that occurs over time as the conductor undergoes bending during numerous charge and discharge cycles.

Superconducting energy storage magnet

A DC to DC converter has a transformer with a highly coupled primary and secondary, a first switch connected in series between a current source and the primary, a second switch connected across the current source in parallel with the first switch and the primary, a rectifier connected to rectify the output of the secondary, an energy storage device such as a capacitor connected to receive the output from the rectifier, and a load connected to receive output voltage across the capacitor. The current source which provides the substantially constant current can be a superconducting storage magnet. The first and second switches are controlled to alternately open and close to provide current through the primary of the transformer to recharge the energy storage device. When voltage across the energy storage capacitor reaches a minimum level, the one of the first and second switches which was closed is opened and the other is closed. This cycle is repeated as the voltage across the output capacitor reaches the minimum value to maintain the output voltage substantially at a constant level.

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Madison, WI, United States of America

Xianrui Huang