Resistor-containing cryogenic current lead

Claim 2

In a superconducting rotor comprising means connected to said rotor for rotation thereof, means in flow communication with the rotor winding chamber of said rotor for supplying liquefied gas thereto as coolant for maintaining rotor windings disposed therein submerged at least in part in a pool of liquefied gas and at cryogenic temperatures, means in flow communication with said chamber for withdrawing coolant vapor therefrom, and means electrically connected to said rotor windings for carrying current between a current distribution device at room temperature and said rotor windings at cryogenic temperatures, the improvement for adapting said rotor for intermittent operation with minimal coolant usage, wherein: (a) a portion of each current-carrying means includes means open at both ends for conducting a confined flow of coolant vapor along and in contact with said current-carrying means, (b) said vapor-conducting means being in flow communication at one open end thereof with a part of said vapor-withdrawing means, (c) said portion having a terminal length thereof extending into said rotor winding chamber, (d) said terminal length being disposed in the generally radial direction locating the other open end of said vapor-conducting means adjacent the wall of said rotor winding chamber, (e) said other open end being submerged below the surface of said pool of liquefied gas during operation to enable liquefied gas to freely enter therein, (f) each current-carrying means includes a current lead having a relatively high lead aspect ratio, and (g) each current lead is provided with resistance means connected in electrical series therewith having relatively high electrical resistance for vaporizing liquefied gas, each resistance means being disposed between the level of liquefied gas within said terminal length and the other open end thereof and in heat exchange relationship with the liquefied gas within said length.

Claim 3

The improvement of claim 1 wherein said lead aspect ratio is greater than that aspect ratio corresponding to the minimum steady-state coolant demand of a lead of the same material and construction in the absence of said resistance means.

Claim 4

The improvement of claim 1 wherein each lead is adapted to carry a current of up to 1000 amps and the value of the lead aspect ratio of each lead is at least 175 cm -1 .

Claim 5

The improvement of claim 3 wherein the resistance value of each resistance means is at least 0.838 micro-ohm.

Claim 6

The improvement of claim 1 wherein the resistance value of the resistance means provided for each lead is sufficient to vaporize the liquid coolant in heat exchange relationship with said resistance means at a sufficient rate such that the resulting vapor flow along said portion prevents thermal failure of said lead.

Claim 7

The improvement of claim 5 wherein said resistance value (R) is at least about 0.00479 times the value of the aspect ratio (LAR) of the lead (exclusive of the resistance means, where the R and LAR values are expressed in micro-ohm and cm -1 units, respectively.

Claim 8

The improvement of claim 1 wherein the resistance means is formed with the transverse area thereof being of substantially the same size and shape as the transverse area of said terminal length, said resistance means being of an electrically conductive material having a higher electrical resistivity than that of the material of which said terminal length is formed.

Claim 9

A pulsed power supply generator including the improved rotor of claim 1.

Claim 10

An aircraft including the generator of claim 8.

Claim 11

In the method of operating a super-conducting rotor driven within a stator assembly wherein liquefied gas is supplied to the rotor winding chamber as the coolant for maintaining the rotor windings at cryogenic temperatures, coolant vapor is withdrawn from said rotor winding chamber and current is carried to and from said rotor windings through current-carrying means, the improvement comprising: employing a current lead having a relatively high lead aspect ratio as at least a portion of said current-carrying means, defining a thermally insulated volume in contact with surface area of each current-carrying means employed along a length thereof, a terminal portion of said volume being positioned in said rotor winding chamber in a location subject to significant centrifugal forces during rotor rotation, said terminal portion of said volume being defined in part by a surface of liquefied gas, said current lead being provided with resistance means having relatively high electrical resistance for vaporizing liquefied gas in heat exchange relationship therewith, said resistance means being connected in electrical series with said lead and disposed below said liquefied gas surface, transferring heat from said resistance means to the liquefied gas in heat exchange relationship therewith and automatically replacing such liquefied gas as it is converted to the vapor phase, said vapor phase being displaced along said thermally insulated volume into a second volume transporting coolant vapor being withdrawn from said rotor winding chamber, said relatively high lead aspect ratio being greater than that aspect ratio corresponding to the minimum steady-state coolant demand of a lead of the same material and construction in the absence of said resistance means, the electrical resistance value of said resistance means being sufficient to vaporize said liquefied gas in heat exchange relationship therewith at a sufficient rate such that the resulting vapor flow substantially prevents thermal failure of said current lead.

Claim 12

In the method of operating a super-conducting rotor driven within a stator assembly wherein liquefied gas is supplied to the rotor winding chamber as the coolant for maintaining the rotor windings at cryogenic temperatures, coolant vapor is withdrawn from said rotor winding chamber and current is carried to and from said rotor windings through current-carrying means, the improvement comprising: employing a current lead having a relatively high lead aspect ratio as at least a portion of said current-carrying means, defining a thermally insulated volume in contact with surface area of each current-carrying means employed along a length thereof, a terminal portion of said volume being positioned in said rotor winding chamber in a location subject to significant centrifugal forces during rotor rotation, said terminal portion of said volume being defined in part by a surface of liquefied gas, said current lead being provided with resistance means having relatively high electrical resistance for vaporizing liquefied gas in heat exchange relationship therewith, said resistance means being connected in electrical series with said lead and disposed below said liquefied gas surface, transferring heat from said resistance means to the liquefied gas in heat exchange relationship therewith and automatically replacing such liquefied gas as it is converted to the vapor phase, said vapor phase being displaced along said thermally insulated volume into a second volume transporting coolant vapor being withdrawn from said rotor winding chamber, said relatively high lead aspect ratio being greater than that aspect ratio corresponding to the minimum steady-state coolant demand of a lead of the same material and construction in the absence of said resistance means, the electrical resistance value of said resistance means being sufficient to vaporize said liquefied gas in heat exchange relationship therewith at a sufficient rate such that the resulting vapor flow substantially prevents thermal failure of said current lead.

Claim 13

The improvement of claim 2 wherein said lead aspect ratio is at least 25% greater than said corresponding aspect ratio.