BACKGROUND OF THE INVENTION
The present invention relates generally to a super-conductive coil in a synchronous
rotating machine. More particularly, the present invention relates to a support
structure for super-conducting field windings in the rotor of a synchronous machine.
Synchronous electrical machines having field coil windings include, but are not
limited to, rotary generators, rotary motors, and linear motors. These machines
generally comprise a stator and rotor that are electromagnetically coupled. The rotor
may include a multi-pole rotor core and one or more coil windings mounted on the
rotor core. The rotor cores may include a magnetically-permeable solid material, such
as an iron-core rotor.
Conventional copper windings are commonly used in the rotors of synchronous
electrical machines. However, the electrical resistance of copper windings (although
low by conventional measures) is sufficient to contribute to substantial heating of the
rotor and to diminish the power efficiency of the machine. Recently, super-
conducting (SC) coil windings have been developed for rotors. SC windings have
effectively no resistance and are highly advantageous rotor coil windings
Iron-core rotors saturate at an air-gap magnetic field strength of about 2 Tesla.
Known super-conductive rotors employ air-core designs, with no iron in the rotor, to
achieve air-gap magnetic fields of 3 Tesla or higher. These high air-gap magnetic
fields yield increased power densities of the electrical machine, and result in
significant reduction in weight and size of the machine. Air-core super-conductive
rotors require large amounts of super-conducting wire. The large amounts of SC wire
add to the number of coils required, the complexity of the coil supports, and the cost
of the SC coil windings and rotor.
High temperature SC coil field windings are formed of super-conducting materials
that are brittle, and must be cooled to a temperature at or below a critical temperature,
e.g., 27°K, to achieve and maintain super-conductivity. The SC windings may be
formed of a high temperature super-conducting material, such as a BSCCO
(BixSrxCaxCuxOx) based conductor.
Super-conducting coils have been cooled by liquid helium. After passing through the
windings of the rotor, the hot, used helium is returned as room-temperature gaseous
helium. Using liquid helium for cryogenic cooling requires continuous reliquefaction
of the returned, room-temperature gaseous helium, and such reliquefaction poses
significant reliability problems and requires significant auxiliary power.
Prior SC coil cooling techniques include cooling an epoxy-impregnated SC coil
through a solid conduction path from a cryocooler. Alternatively, cooling tubes in the
rotor may convey a liquid and/or gaseous cryogen to a porous SC coil winding that is
immersed in the flow of the liquid and/or gaseous cryogen. However, immersion
cooling requires the entire field winding and rotor structure to be at cryogenic
temperature. As a result, no iron can be used in the rotor magnetic circuit because of
the brittle nature of iron at cryogenic temperatures.
What is needed is a super-conducting field winding assemblage for an electrical
machine that does not have the disadvantages of the air-core and liquid-cooled super-
conducting field winding assemblages of, for example, known super-conductive
rotors.
In addition, high temperature super-conducting (HTS) coils are sensitive to
degradation from high bending and tensile strains. These coils must undergo
substantial centrifugal forces that stress and strain the coil windings. Normal
operation of electrical machines involves thousands of start-up and shut-down cycles
over the course of several years that result in low cycle fatigue loading of the rotor.
Furthermore, the HTS rotor winding should be capable of withstanding 25% over-
speed operation during rotor balancing procedures at ambient temperature, and
notwithstanding occasional over-speed conditions at cryogenic temperatures during
power generation operation. These over-speed conditions substantially increase the
centrifugal force loading on the windings over normal operating conditions.
SC coils used as the HTS rotor field winding of an electrical machine are subjected to
stresses and strains during cool-down and normal operation. They are subjected to
centrifugal loading, torque transmission, and transient fault conditions. To withstand
the forces, stresses, strains and cyclical loading, the SC coils should be properly
supported in the rotor by a coil support system. These support systems hold the SC
coil(s) in the HTS rotor and secure the coils against the tremendous centrifugal forces
due to the rotation of the rotor. Moreover, the coil support system protects the SC
coils, and ensures that the coils do not prematurely crack, fatigue or otherwise break.
Developing support systems for HTS coil has been a difficult challenge in adapting
SC coils to HTS rotors. Examples of coil support systems for HTS rotors that have
previously been proposed are disclosed in U.S. Patents Nos. 5,548,168; 5,532,663;
5,672,921; 5,777,420; 6,169,353. and 6,066,906. However, these coil support
systems suffer various problems, such as being expensive, complex and requiring an
excessive number of components. There is a long-felt need for a HTS rotor having a
coil support system for a SC coil. The need also exists for a coil support system made
with low cost and easy-to-fabricate components.
BRIEF SUMMARY OF THE INVENTION
A coil support system has been developed for a race-track shaped, high temperature
super-conducting (HTS) coil winding for two-pole rotor of an electrical machine. The
coil support system prevents damage to the coil winding during rotor operation,
supports the coil winding with respect to centrifugal and other forces, and provides a
protective shield for the coil winding. The coil support system holds the coil winding
with respect to the rotor. The HTS coil winding and coil support system are at
cryogenic temperature while the rotor is at ambient temperature.
The coil support system includes a series of coil support assemblies that span between
opposite sides of the race-track coil winding. Each coil support assembly includes a
tension rod, a pair of tension bolts and a pair of channel housings. The tension rods
extend between opposite sides of the coil winding through conduits, e.g., holes, in the
rotor core. Tension bolts are inserted into both ends of the tension rod. The tension
bolts provide a length adjustment of the coil support assembly that is useful to
compensate for variations in coil geometry. Each bolt is fastened to one of the pair of
channel housings. Each housing fits around the HTS coil. Each coil support
assembly braces the coil winding with respect to the rotor core. The series of coil
support assemblies provides a solid and protective support for the coil winding.
The HTS rotor may be for a synchronous machine originally designed to include SC
coils. Alternatively, the HTS rotor may replace a copper coil rotor in an existing
electrical machine, such as in a conventional generator. The rotor and its SC coils are
described here in the context of a generator, but the HTS coil rotor is also suitable for
use in other synchronous machines.
The coil support system is useful in integrating the coil support system with the coil
and rotor. In addition, the coil support system facilitates easy pre-assembly of the coil
support system, coil and rotor core prior to final rotor assembly. Pre-assembly
reduces coil and rotor assembly time, improves coil support quality, and reduces coil
assembly variations.
In a first embodiment, the invention is a rotor for a synchronous machine comprising:
a rotor core; a super-conducting coil winding extending around at least a portion of
the rotor, said coil winding having a side section adjacent a side of the rotor core; at
least one tension rod extending through a conduit in said rotor; at least one tension
bolt is inserted into an end of the tension rod; and a housing attached to the tension
bolt and bracketing the side section of the coil winding.
In another embodiment, the invention is a method for supporting a super-conducting
coil winding in the rotor core of a synchronous machine comprising the steps of:
extending a tension rod through a conduit in said rotor core; inserting at least one
tension bolt into an end of the rod; positioning the coil winding around the rotor core
such that the tension rod and tension bolt span between side sections of the coil
winding; assembling at least one channel housing around one of the side sections of
the coil winding, and securing the bolt to one of the channel housings.
A further embodiment of the invention is a rotor for a synchronous machine
comprising: a rotor core having a conduit orthogonal to a longitudinal axis of the
rotor; a race-track, super-conducting (SC) coil winding in a planar race-track parallel
to the longitudinal axis of the rotor; a tension rod inside the conduit of the core; a
tension bolt in each end of said tension rod, and a housing coupling opposite sides of
the coil winding to the tension bolts.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings in conjunction with the text of this specification describe
an embodiment of the invention.
FIGURE 1 is a schematic side elevational view of a synchronous electrical machine
having a super-conductive rotor and a stator.
FIGURE 2 is a perspective view of an exemplary race-track, super-conducting coil
winding.
FIGURE 3 is a partially cut-away view of the rotor core, coil winding and coil support
system for a high temperature super-conducting (HTS) rotor.
FIGURE 4 is a perspective view of the rotor core, coil winding and coil support
system for a high temperature super-conducting (HTS) rotor.
DETAILED DESCRIPTION OF THE INVENTION
FIGURE 1 shows an exemplary synchronous generator machine 10 having a stator 12
and a rotor 14. The rotor includes field winding coils that fit inside the cylindrical
rotor vacuum cavity 16 of the stator. The rotor fits inside the rotor vacuum cavity of
the stator. As the rotor turns within the stator, a magnetic field 18 (illustrated by
dotted lines) generated by the rotor and rotor coils moves/rotates through the stator
and creates an electrical current in the windings of the stator coils 19. This current is
output by the generator as electrical power.
The rotor 14 has a generally longitudinally-extending axis 20 and a generally solid
rotor core 22. The solid core 22 has high-magnetic permeability, and is usually made
of a ferromagnetic material, such as iron. In a low-power density super-conducting
machine, the iron core of the rotor is used to reduce the magnetomotive force (MMF),
and, thus, minimize the amount of super-conducting (SC) coil wire needed for the coil
winding. For example, the solid iron-rotor core may be magnetically saturated at an
air-gap magnetic field strength of about 2 Tesla.
The rotor 14 supports at least one longitudinally-extending, race-track-shaped, high-
temperature super-conducting (HI'S) coil winding 34 (See Fig. 2). The HIS coil
winding may be alternatively a saddle-shape or have some other shape that is suitable
for a particular HTS rotor design. A coil support system is disclosed here for a race-
track SC coil winding. The coil support system may be adapted for coil
configurations other than a race-track coil mounted on a solid rotor core.
The rotor includes a collector end shaft 24 and a drive end shaft 30 that both bracket
the rotor core 22 and are supported by bearings 25. The collector end shaft includes
collector rings 78 for electrically connecting to the rotating SC coil winding. The
collector end shaft 24 also has a cryogen transfer coupling 26 to a source of cryogenic
cooling fluid used to cool the SC coil windings in the rotor. The cryogen transfer
coupling 26 includes a stationary segment coupled to a source of cryogen cooling
fluid and a rotating segment which provides cooling fluid to the HTS coil. The drive
end shaft 30 may be driven by a power turbine via drive coupling 32.
FIGURE 2 shows an exemplary HTS race-track field coil winding 34. The SC field
winding coils 34 of the rotor includes a high temperature super-conducting (SC) coil
36. Each SC coil includes a high temperature super-conducting conductor, such as a
BSCCO (BixSrxCaxCuxOx) conductor wires laminated in a solid epoxy impregnated
winding composite. For example, a series of BSCCO 2223 wires may be laminated,
bonded together and wound into a solid epoxy impregnated coil.
SC wire is brittle and easy to be damaged. The SC coil is typically layer wound SC
tape that is epoxy impregnated. The SC tape is wrapped in a precision coil form to
attain close dimensional tolerances. The tape is wound around in a helix to form the
race-track SC coil 36.
The dimensions of the race-track coil are dependent on the dimensions of the rotor
core. Generally, each race-track SC coil encircles the magnetic poles of the rotor
core, and is parallel to the rotor axis. The coil windings are continuous around the
race-track. The SC coils form a resistance-free electrical current path around the rotor
core and between the magnetic poles of the core. The coil has electrical contacts 114
that electrically connect the coil to the collector 78.
Fluid passages 38 for cryogenic cooling fluid are included in the coil winding 34.
These passages may extend around an outside edge of the SC coil 36. The
passageways provide cryogenic cooling fluid to the coil and remove heat from the
coil. The cooling fluid maintains the low temperatures, e.g., 27°K, in the SC coil
winding needed to promote super-conducting conditions, including the absence of
electrical resistance in the coil. The cooling passages have an input and output fluid
ports 112 at one end of the rotor core. These fluid (gas) ports 112 connect the cooling
passages 38 on the SC coil to the cryogen transfer coupling 26.
Each HTS race-track coil winding 34 has a pair of generally-straight side portions 40
parallel to a rotor axis 20, and a pair of end portions 54 that are perpendicular to the
rotor axis. The side portions of the coil are subjected to the greatest centrifugal
stresses. Accordingly, the side portions are supported by a coil support system that
counteract the centrifugal forces that act on the coil.
FIGURE 3 shows a partially cut away view of a rotor core 22 and coil support system
for a high temperature super-conducting (HTS) coil winding. The coil support
systems includes a series of coil support assemblies spanning through the rotor core
and between opposite sides of the HTS coil winding. Each coil support assembly
comprises a tension rod 42 that extends through the rotor core, tension bolts 43
inserted into the ends of the rod, and channel coil housings 44 fastened to the bolts
and that bracket the coil windings. The coil support system provides a structural
frame to hold the coil winding in the rotor.
The principal loading of the HTS coil winding 34 is from centrifugal acceleration
during rotor rotation. The coil support assemblies are each aligned with the
centrifugal loading of the coil to provide effective structural support to the coil
winding under load. To support the side sections of the coil, each assembly of a
tension rod 42 and bolts 43 (tension rod assembly) spans between the coils, and
attaches to the channel coil housings 44. The housings grasp opposite side sections of
the coil. The tension rods 42 extend through a series of conduits 46 in the rotor core.
These rods are aligned with the quadrature axis of the rotor core.
The channel coil housings 44 support the coil winding 34 against centrifugal forces
and tangential torque forces. Centrifugal forces arise due to the rotation of the rotor.
Tangential forces may arise from acceleration and deceleration of the rotor, and
torque transmission. Because the long sides 40 of the coil winding are encased by the
channel housings 44 and the ends 86 of the tension bolts, the sides of the coil winding
are fully supported within the rotor.
The conduits 46 are generally cylindrical passages in the rotor core having a straight
axis. The diameter of the conduits is substantially constant. However, the ends 88 of
the conduits may expand to a larger diameter to accommodate an insulating tube 52.
This tube aligns the rod 42 in the conduit and provides thermal isolation between the
rotor core and the rod. The insulating tube has a lower outer ring 123 that engages the
walls of the wide diameter end 88 of the rotor conduits 46. The cylindrical side wall
121 of the insulating tube 52 extends up from the outer ring 123, and is not in contact
with the walls of the conduit. The upper end of the tube engages a lock-nut 84 that
connects the tube to the tension rod 42. Thus, the insulating tube and lock-nut
provide a non-thermally conducting mount for the tension rod in the conduits 46 of
the rotor core.
The number of conduits 46 and their location on the rotor core depends on the
location of the HTS coils and the number of coil housings needed to support the side
sections of the coils. The axes of the conduits 46 are generally in a plane defined by
the race-track coil 34. In addition, the axes of the conduits are perpendicular to the
side sections of the coil. Moreover, the conduits are orthogonal to and intersect the
rotor axis, in the embodiment shown here. The number of conduits and the location
of the conduits will depend on the location of the HTS coils and the number of coil
housings needed to support the side sections of the coils.
There are generally two categories of support for super-conducting winding: (i)
"warm" supports and (ii) "cold" supports. In a warm support, the supporting
structures are thermally isolated from the cooled SC windings. With warm coil
supports, most of the mechanical load of a super-conducting (SC) coil is supported by
structural members that span between the cold coils and the warm support members.
In a cold coil support system, the support system is at or near the cold cryogenic
temperature of the SC coils. In cold supports, most of the mechanical load of a SC
coil is supported by the coil support structural members which are at or near
cryogenic temperature.
The exemplary coil support system disclosed here is a cold support in that the tension
rods 42, bolts 43 and associated channel housings 44 are maintained at or near a
cryogenic temperature. Because the coil support members are cold, these members
are thermally isolated, e.g., by the non-contact conduits through the rotor core, from
the rotor core and other "hot" components of the rotor.
The HTS coil winding and structural coil support components are all at cryogenic
temperature. In contrast, the rotor core is at an ambient "hot" temperature. The coil
supports are potential sources of thermal conduction that would allow heat to reach
the HTS coils from the rotor core. The rotor core becomes hot during operation. As
the coil windings are to be held in super-cooled conditions, heat conduction into the
coils from core is to be avoided.
The coil support system is thermally isolated from the rotor core. For example, the
tension rods and bolts are not in direct contact with the rotor. This lack of contact
avoids the conduction of heat from the rotor to the tension rods and coils. In addition,
the mass of the coil support system structure has been minimized to reduce the
thermal conduction through the support assemblies into the coil windings from the
rotor core.
Each tension rod 42 is a shaft with continuity along the longitudinal direction of the
rod and in the plane of the race-track coil. The tension rod is typically made of high
strength non-magnetic alloys such as titanium, aluminum or an Inconel alloy. The
longitudinal continuity of the tension rods provides lateral stiffness to the coils which
provides rotor dynamics benefits. Moreover, the lateral stiffness of the tension rods
42 permits integrating the coil support with the coils so that the coil can be assembled
with the coil support on the rotor core prior to final rotor assembly.
The tension bolts 43 screw into threaded holes 120 in the end of the tension rod. The
depth to which the bolt screws into the rod is adjustable. The total length of the
tension rod and bolt assembly (which assembly spans between the sides of the coil)
can be changed by turning one or both of the bolts into or out of the holes of the
tension rods. This adjustment in the length of the tension rod and bolts assembly is
useful in fitting this assembly between the sides of a coil winding. The depth of the
threaded hole in the end of the tension rod is sufficient to provide adequate adjustment
of the length of the tension rod and bolts assembly.
The head 122 of the bolt includes a flange with a flat outer surface 86. The flat head
86 of the bolt abuts an inside surface of the coil winding 34 and, thus, supports the
load on the coil winding that is parallel to the tension rod.
The flat surface 86 of the bolt head supports an inside surface of a side of the coil
winding. The other three surfaces of the side 40 of the coil winding are supported by
the channel housing 44. Each coil channel housing is assembled around the coil and
forms a coil casing in cooperation with the bolt head. This casing supports the coil
winding with respect to tangential and centrifugal loads. The casing also allows the
coil winding to expand and contract longitudinally.
Each channel housing 44 has a pair of side panels 124, a wedge 126 and a threaded
insert sleeve 128. The side panels bracket opposite surfaces of the coil. An inside
surface of each side panel has a narrow slot 130 to receive the wedge and an "L"
shaped surface 132 to receive a side surface of the coil winding. The inside surface of
each side panel also has a threaded flange 134 that includes a lip 135 of the L-surface
132 to engage a corner of the coil winding. The threaded section of the flange engage
a threaded insert 128 that fits between the flange sections 134 of the opposite side
panels 124. The insert has an aperture 137 with a rim to receive the tension bolt 43.
A lock-nut 138 holds the insert 128 securely against the bolt head 43.
The wedge 126 fits into the narrow slot 130 of each side panel and spans between the
side panels. The wedge abuts an outside surface: of the coil and has a channel 136 to
receive the cooling passage 38 on the outside surface of the coil. Locking screws 140
hold the side panels to the wedge. The side panels are held together by the wedge and
grasp the treaded insert which is secured to the bolt head. The channel housing may
be made of light, high strength material that is ductile at cryogenic temperatures.
Typical materials for the channel housings are aluminum and titanium alloys. The
shape of the channel housing has been optimized for low weight.
As shown in FIGURE 4, a series of channel coil housings 44 (and associated tension
bolts 43 and rods 44) may be positioned along the sides 40 of the coil winding. The
channel housings collectively distribute the forces that act on the coil, e.g., centrifugal
forces, over substantially the entire side sections 40 of the coil. The channel housings
44 prevent the coil side sections 40 from excessive flexing and bending due to
centrifugal forces.
The plurality of channel housings 44 effectively hold the coil in place without
affectation by centrifugal forces. Although the channel housings are shown as having
a close proximity to one another, the housings need only be as close as necessary to
prevent degradation of the coil caused by high bending and tensile strains during
centrifugal loading, torque transmission, and transient fault conditions.
The coil supports do not restrict the coils from longitudinal thermal expansion and
contraction that occur during normal start/stop operation of the gas turbine. In
particular, thermal expansion is primarily directed along the length of the side
sections Thus, the side sections of the coil slide slightly longitudinally with respect
to the channel housing and tension rods.
The coil support system of tension rods 42, bolts 43 and channel housings 44 may be
assembled with the HTS coil windings 34 as they are mounted on the rotor core 22.
The tension rods and channel housings provide a fairly rigid structure for supporting
the coil winding and holding the long sides of the coil winding in place with respect to
the rotor core. The ends of the coil may be supported by split clamps 58 at the axial
ends of (but not in contact with) the rotor core 22.
The iron rotor core 22 has a generally cylindrical shape suitable for rotation within the
rotor cavity 16 of the stator 12. To receive the coil winding, the rotor core has
recessed surfaces 48, such as flat or triangular regions or slots. These surfaces 48 are
formed in the curved surface of the cylindrical core and extending longitudinally
across the rotor core. The coil winding 34 is mounted on the rotor adjacent the
recessed areas 48. The coils generally extend longitudinally along an outer surface of
the recessed area and around the ends of the rotor core. The recessed surfaces 48 of
the rotor core receive the coil winding. The shape of the recessed area conforms to
the coil winding. For example, if the coil winding has a saddle-shape or some other
shape, the recess(es) in the rotor core would be configured to receive the shape of the
winding.
The recessed surfaces 48 receive the coil winding such that the outer-surface of the
coil winding extends to substantially an envelops: defined by the rotation of the rotor.
The outer curved surfaces 50 of the rotor core when rotated define a cylindrical
envelope. This rotation envelope of the rotor has substantially the same diameter as
the vacuum rotor cavity 16 (see Fig. 1) in the stator.
The gap between the rotor envelope and stator cavity 16 is a relatively-small
clearance, as required for forced flow ventilation cooling of the stator only, since the
rotor requires no ventilation cooling. It is desirable to minimize the clearance
between the rotor and stator to increase the electromagnetic coupling between the
rotor coil windings and the stator windings. Moreover, the rotor coil winding is
preferably positioned such that it extends to the envelope formed by the rotor and,
thus, is separated from the stator by only the clearance gap between the rotor and
stator.
At the end of each tension rod, there may be an insulating tube 52 that fastens the coil
support structure to the hot rotor and prevents heat convection therebetween.
Additionally, there may an insulating lock-nut 84 connected to the insulating tube 52,
and that further facilitates the connection between the tension rod and the housing.
The lock-nut 84 and the tube 52 secure the tension rod and channel housing to the
rotor core while minimizing the heat transfer from the hot rotor to the housing
structure.
The rotor core, coil windings and coil support assemblies are pre-assembled. Pre-
assembly of the coil and coil support reduces production cycle, improves coil support
quality, and reduces coil assembly variations. Before the rotor core is assembled with
the rotor end shafts and other components of the rotor, the tension rods 42 are inserted
into each of the conduits 46 that extend through the rotor core. The insulator tube 52
at each end of each tension rod is placed in the expanded end 88 at each end of the
conduits 46. The tube 52 is locked in place by a retainer locking-nut 84.
The bolts 43 may be inserted before or after the tension rods are inserted into the rotor
core conduits. The treaded inserts 128 and locking nut 138 are placed on the bolts 43
before the bolts are placed in the tension rods. However, the lock-nut is not tightened
against the insert until after the channel housing 44 is assembled.
The depth to which the bolts are screwed into the tension rods is selected such that the
length from the end of one bolt on a tension rod to the end of the opposite bolt clears
the distance between the assembly of channel housings over the long sides 40 of the
coil winding. When the tension rods and bolts are assembled in the rotor core 22, the
coil winding 34 is ready to be inserted onto the core.
The channel housings 44 are assembled over the winding 34. The lock screws are
inserted to hold the wedges and the side panels together. Then the subassembly of
coil winding and channel housings is inserted onto the rotor core over the ends of the
tension rods 42. The cylindrical threaded insert 128 is screwed or otherwise inserted
between the side panels so that the flat end of the bolt head abut the inside surface of
the side sections 40 of the winding. The lock-nut 138 is used to tighten the threaded
insert against the bolt.
The rotor core may be encased in a metallic cylindrical shield 90 (shown by dotted
lines) that protects the super-conducting coil winding 34 from eddy currents and other
electrical currents that surround the rotor and provides a vacuum envelope to maintain
a hard vacuum around the cryogenic components of the rotor. The cylindrical shield
90 may be formed of a highly-conductive material, such as a copper alloy or
aluminum.
The SC coil winding 34 is maintained in a vacuum. The vacuum may be formed by
the shield 90 which may include a stainless steel cylindrical layer that forms a vacuum
vessel around the coil and rotor core.
The coil channel housings, tension rods and bolts (coil support assembly) may be
assembled with the coil winding before the rotor core and coils are assembled with the
collar and other components of the rotor. Accordingly, the rotor core, coil winding
and coil support system can be assembled as a unit before assembly of the other
components of the rotor and of the synchronous machine.
While the invention has been described in connection with what is presently
considered to be the most practical and preferred embodiment, it is to be understood
that the invention is not to be limited to the disclosed embodiment, but on the
contrary, is intended to cover all embodiments within the spirit of the appended
claims.
WE CLAIM
1. A rotor (14) for a synchronous machine (10),comprising :
a rotor core (22);
a super-conducting coil winding (34) extending around at least a portion
of the rotor core (22), said coil winding (34) having a side section (40)
adjacent a side of the rotor core (22); characterized by comprising:
at least one tension rod (42) extending through a conduit (46) in said
rotor core (22);
at least one tension bolt (43) extending between an end of the tension
rod (42) and the side section (40) of the coil winding (34); and
a channel housing (44) attached to the tension bolt (43) and connected to
the side section (40) of the coil winding (34).
2. A rotor as claimed in claim 1, wherein said housing (44) comprises a pair
of side panels (124) on opposite surfaces of the side section (40).
3. A rotor as claimed in claim 1, wherein said housing (44), bolt (43) and
tension rod (42) are cooled by conduction from said coil winding (34).
4. A rotor as claimed in claim 1, wherein a depth of the bolt (43) in the
tension rod (42) is adjustable.
5. A rotor as claimed in claim 1, wherein the bolt (43) comprises a head
(122) having a flat surface (86) abutting the coil (34).
6. A rotor as claimed in claim 1, comprising a second bolt (43) extending
from a second end of the tension rod (42) and abutting a second side
section of the coil winding (34).
7. A rotor as claimed in claim 1, wherein the housing (44) comprises side
panels (124) bracketing the side section (40) of the coil (34), and a wedge
(126) between the side panels (124) and abutting an outside surface of
the side section (40).
8. A rotor as claimed in claim 1, wherein the bolt (43) has a flat head (122)
abutting the coil winding (34).
9. A rotor as claimed in claim 1, wherein said housing (44) is formed of a
metal material selected from a group consisting of aluminum and a
titanium alloy.
10. A rotor as claimed in claim 1, wherein said tension rod (42) is formed of a
non-magnetic metal alloy.
11.A rotor as claimed in claim 1, wherein said tension rod (42) is formed of
an Inconel alloy.
12.A rotor as claimed in claim 1, wherein the rotor core has an axis, the
tension rod and the conduit extending from the side section of the coil
winding to an opposite side section side section of the coil winding, the
tension rod being perpendicular to the axis of the rotor core.
13. A rotor for a synchronous machine comprising:
a rotor core (22) having a conduit (46);
a race-track super-conducting coil winding (34) in a plane parallel to a
longitudinal axis (20) of the rotor core (22);
a tension rod (42) in the conduit (46) of the core (22);
a tension bolt (43) in each end of said tension rod (42); and
a housing (44) coupling the coil winding (34) to each tension bolt (43).
14. A rotor as claimed in claim 13, wherein the rotor core (22) has a plurality
of conduits (46) orthogonal to the longitudinal axis (20) of the rotor core
(22) and in the plane defined by the coil winding (34).
15. A rotor as claimed in claim 13, wherein each tension bolt (43) has an end
surface abutting the coil winding (34).
16. A rotor as claimed in claim 13, wherein the housing (44) comprises a pair
of side panels (124) on opposite surfaces of the coil winding (34), a
wedge (126) connecting the side panels (124), and a threaded insert
(128) coupled to the side panels (124) and secured to the tension bolt
(43).
17. A rotor as claimed in claim 12, comprising an insulating tube sleeve (52)
between the rotor core (22) and the tension rod (42).

This invention relates to a rotor (14) is disclosed for a synchronous machine (10)
comprising: a rotor core (22); a super-conducting coil winding (34) extending
around at least a portion of the rotor core (22), said coil winding (34) having a
side section (40) adjacent a side of the rotor core (22); at least one tension rod
(42) extending through a conduit (46) in said rotor core (22); at least one
tension bolt (43) extending between an end of the tension rod (42) and abutting
the side section (40) of the coil winding (34); and a channel housing (44)
attached to the tension bolt (43) and the coil winding (34).