General Atomics, Inc.

Michael Heiberger

Michael Robert Reed

Alan Robert Langhorn

William Patrick Creedon

Edward E Bowles

Dean G Morris

A homopolar machine produces an axial counter force on the rotating shaft to compensate for the load on the shaft's thrust bearing to reduce wear and noise and prolong bearing life. The counter force is produced through magnetic interaction between the shaft and the machine's field coils and is created by changing the current excitation of the field coils, which results in a magnetic flux asymmetry in an inner flux return coupled to the shaft. The homopolar machine may also have a configuration that uses current collectors that maintain substantially constant contact pressure in the presence of high magnetic fields to improve current collector performance. The current collectors are flexible and may be made from either electrically conductive fibers or stacked strips such that they bear up against the armature so that the pressure is maintained by the spring constant of the current collector material. The homopolar machine may also have a configuration where the brushes are oriented so that the current is aligned as much as is practical with the local magnetic field lines so as to reduce the lateral electromagnetic forces on the brushes.

Homopolar machine with shaft axial thrust compensation for reduced thrust bearing wear and noise

A homopolar machine produces an axial counterforce on the rotating shaft to compensate for the load on the shaft's thrust bearing to reduce wear and noise and prolong bearing life. The counterforce is produced through magnetic interaction between the shaft and the machine's field coils and is created by changing the current excitation of the field coils, which results in a magnetic flux asymmetry in an inner flux return coupled to the shaft. The homopolar machine may also have a configuration that uses current collectors that maintain substantially constant contact pressure in the presence of high magnetic fields to improve current collector performance. The current collectors are flexible and may be made from either electrically conductive fibers or stacked strips such that they bear up against the armature so that the pressure is maintained by the spring constant of the current collector material.

Reduction of induced magnetic forces on current collectors in homopolar machines having high magnetic fields

A superconductor device which including a magnet coil assembly and support structures. The magnet coil assembly consists of superconducting wire which is encased in a composite structure along with an integral thermal interface. This combination forms the magnet coil assembly. The magnet coil assembly is cooled to an operating temperature of about 5K with a conductive cooling device that physically connects with the thermal interface integral to the magnet coil assembly. A cold-to-warm support structure supports the magnet coil assembly within a vacuum vessel while thermally isolating it from the external environment Structurally, the magnet coil assembly is cylindrically shaped and positioned within a toriodal shaped thermal shield which is positioned within a toroidal shaped vacuum vessel. The cold-to-warm support structure supports the magnet coil assembly spaced apart from the thermal shield. The cold-to-warm support structure includes a tapered section and an annular section. The tapered section is shaped as a truncated cone and is attached to a proximal end of the vacuum vessel. The tapered cone extends distally and projects radially into the vacuum chamber. The tapered cone passes through an interface in the thermal shield and is connected to a second end of the annular section. The annular section extends proximally from the tapered section and includes a first end that is connected to the magnet coil assembly.

Inner cold-warm support structure for superconducting magnets

A demountable thermal coupling for engaging a refrigeration unit with a cryogenic device includes a collet assembly which is slidingly mounted against a retainer ring in the passageway of a sleeve assembly. When the refrigeration unit is engaged with the sleeve assembly, the collet assembly closes onto a cooling probe of the refrigeration unit to establish a thermal contact between the cooling probe and the collet assembly. An interconnect between the collet and the superconducting device then allows the cooling probe to cool the superconducting device. Withdrawal of the cooling probe from the collet disengages the refrigeration unit from the superconducting device.

Demountable thermal coupling and method for cooling a superconductor

A shuntable low loss variable current vapor cooled lead (VCVCL) configuration delivers current to and from a superconductive load, such as a superconductive magnet, immersed in a cryogenic liquid in a way that minimizes the boil-off rate of the cryogenic liquid. The VCVCL configuration includes superconductive lead assemblies containing superconductive segments. The assemblies are connected in parallel between the superconductive load and an output current source or sink. Each assembly is controlled so that its superconducting segment is either superconducting or non-superconducting. By selectively controlling whether each lead assembly is superconducting or non-superconducting, by varying the cryogenic liquid level, the current flow to or from the superconducting load through the lead assemblies is shunted from those lead assemblies exhibiting a relatively high resistance to those having a relatively low resistance, and the current is selectively distributed between superconducting lead assemblies so that each lead assembly either carries near zero current or an optimum current. At near zero current, the lead assembly contributes very little to the helium boil-off rate because of negligible Joule heating, and because the path of thermal conduction to the liquid helium is significantly more resistive. At or near the optimum current, the helium boil-off rate approaches a theoretical minimum. By keeping the current in each lead assembly at near zero or near the optimum design current, the helium boil-off rate of the VCVCL configuration is minimized and is significantly less than that of conventionally designed lead arrays.

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San Diego, CA, United States of America

Michael Heiberger