BACKGROUND OF THE INVENTION
The present invention relates generally to a superconductive coil in a synchronous
rotating machine. More particularly, the present invention relates to an apparatus and
method for manufacturing superconducting 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 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. Electrical resistance of copper windings, however, is sufficient
(although low by conventional measures) to contribute to substantial heating of the
rotor and to diminish the power efficiency of the machine. Recently, superconducting
coil windings have been developed for rotors, which have effectively no resistance
and are highly advantageous rotor coil windings.
High temperature superconducting coils used as the rotor field windings of the
electncal machine must be designed as rigid structures made with precise dimensional
tolerances so that the structural support can fit to the coil without excessive clearances
that may result in high strain and potential damage to the coil during loading. The
spring back of the tape conductor as it is wound on the straight sections of a racetrack
coil form results in poor packing factor and lower strength of the composite compared
to the circular sections.
Typical superconductor rotor windings are made from saddle-shaped coils that are
assembled around cylindrical shells for structural support. These saddle-shaped coils

are complex winding structures that may result in overstraining the high temperature
superconducting (HTS) tape conductor by the winding operation as a result of tight
bend diameters, twisting of leads, and differential thermal strain of the winding
relative to the support structure during cool down.
BRIEF SUMMARY OF THE INVENTION
In an exemplary embodiment of the invention, an apparatus for manufacturing HTS
coils includes two side plates disposed in facing relation, a preferably racetrack-
shaped bobbin disposed between the side plates that receives layers of HTS tape
interposed with a binder, and a plurality of blocks assembled adjacent an outer edge
of the side plates. The blocks are displaceable toward the bobbin to compress the
layers of HTS tape on the bobbin. The plurality of blocks may be assembled on the
outer edge of the side plates via bolts. In this context, the bolts are sized to stepwise
compress the layers of HTS tape. Alternatively, the blocks may include blocks of
different thicknesses for selective compressing according to a number of layers of the
HTS tape. Still further, the plurality of blocks may include a plurality of final blocks
that are shaped according to desired outside dimensions of the superconducting coils.
The binder may be any suitable material and preferably includes pre-preg filament-ply
interlayer insulation or a thermoplastic material.
In another exemplary embodiment of the invention, a method of manufacturing HTS
coils is performed with the apparatus of the invention. The method includes the steps
of (a) winding HTS tape onto the bobbin, (b) applying a binder to the wound HTS
tape, (c) compressing the IITS tape and the binder against the bobbin with the
plurality of blocks, and (d) baking the compressed HTS tape and the binder to thereby
cure the binder. Steps (a), (b) and (c) may be practiced for each layer of HTS tape.
Alternatively, steps (b) and (c) may be practiced after winding multiple layers of the
HTS tape. In this context, step (b) may be practiced by epoxy-impregnating the
wound multiple layers of the HTS tape by a vacuum pressure impregnation process.
Still further, step (a) in this context may be practiced using HTS tape with a pre-preg
coating.
The method may further include, prior to step (a), the step of securing a start lead of
the coil to a lead terminal on one of the two side plates and applying a binder layer to
the bobbin. In this context, prior to step (d), the method may additionally include the
step of securing a finished lead of the coil to a lead terminal on the other of the two
side plates, applying a layer of copper foil to the coil with a rectangular cooling heat
exchanger tube bonded thereto, and repeating step (c) under heat.
BRIEF DESCRIPTION OF THE ACCOMPAYING DRAWINGS

FIGURE 1 is an assembly drawing showing the apparatus and method for
manufacturing HTS racetrack coil of the invention; and
FIGURE 2 is a perspective view of the apparatus,
DETAILED DESCRIPTION OF THE INVENTION
FIGURES 1 and 2 illustrate a precision coil form 10 used for fabricating high
temperature superconducting (HTS) coil. The HTS coil is typically layer wound with
HTS tape under tension on the coil form and is epoxy-impregnated and compressed to
attain close dimensional tolerances. Several types of HTS tape are known, and any
suitable HTS tape could be used in the manufacture of the HTS coil of the invention.
The coil form 10 includes a racetrack-shaped bobbin 12 with substantially straight
sides as shown and two side plates 14 that are disposed in facing relation surrounding
the bobbin 12. The plates 14 may include impregnation holes {not shown) to effect
post-compression epoxy impregnation of the HTS tape winding. A series of blocks
16 are assembled on an outer edge of the side plates 14 and are displaceable toward
and away from the bobbin 12 via bolts or the like. The HTS tape winding is shown in
FIGURE 1 at 18.
In manufacturing the HTS coil, a start lead of the coil is soldered to a lead terminal,
such as a copper lead terminal or the like, that is secured to one of the side plates 14
near the center line axis of the coil. A layer of binder such as pre-preg filament plies
or a thermoplastic material such as polyester is applied on the bobbin 12, then a first
layer of the HTS tape is wound. The blocks 16 are bolted on the side plates 14,

particularly at least the straight blocks, to compress the straight sections of the first
layer against the bobbin 12 so that the first layer of tape, the pre-preg layer, and the
bobbin 12 all stick together. A second layer of binder material (pre-preg filament
plies) is applied on top of the first tape layer, then a second layer of IITS tape is
wound. The same series of straight blocks 16 is used to compress the winding 18
against the bobbin 12 so that all the layers stick together. The layer winding process
continues until the last odd number layer is complete, and a finish lead is soldered to a
copper lead terminal that is secured to the other of the side plates 14 near the center
line axis of the coil.
A layer of pre-preg filament plies is then applied on the outside surface of the
complete winding followed by a layer of copper foil with a rectangular cooling heat
exchanger tube bonded on the outside surface. A series of straight blocks and corner
blocks 16 (as shown in FIGURE 1) are assembled to the outside surface of the copper
foil via the side plates 16 to compress the complete coil as moderate heat is applied to
precision shape the coil outside surface. The finished coil form and winding assembly
is baked at uniform temperature to cure the pre-preg. The temperature varies
according to a curing temperature of the particular material. The resulting coil
structure is a strong winding composite built to close tolerance dimensions.
In the manufacturing process, the bolts that secure the blocks 16 to the side plates 14
may be sized to effect stepwise compression of the layers of HTS tape. In this
manner, only one production set of blocks 16 is required as the bolts enable stepwise
compression of the IITS tape as the layers are formed. Alternatively, the plurality of
blocks may include blocks of different thicknesses for selective compressing
according to a number of layers of the HTS tape. The blocks may additionally
include a plurality of final blocks that are shaped according to a desired outside
diameter of the superconducting coils (as shown in FIGURE 2) to effect a precisely
sized coil form.
In a variation of the winding fabrication process, a pre-preg coating on the HTS tape
insulation is used, thereby eliminating the interlayer pre-preg filament plies. The
resulting coil structure has higher packing factor of HTS tapes, resulting in higher
winding current density. In another alternative, glass insulated HTS tape can be used
with a fast curing adhesive to bond and compress each layer to the one before at
discrete locations. Subsequently, the complete winding is epoxy-impregnated by a
vacuum pressure impregnation process. The vacuum pressure impregnation process
is known, and details thereof will not be provided.
With the structure and method of the present invention, each layer of wound HTS tape
can be bonded and compressed with the one before so that spring back of the tape on
at least the straight sections is eliminated, thus preventing poor packing factor,
reduced current density and inferior strength properties of the winding composite.
The HTS coil fabricated with the apparatus and method of the invention results in a
precision coil form that prevents high strains and potential damage to the coil during
loading.
While the invention has been described in connection with what is presently
considered to be the most practical and preferred embodiments, it is to be understood
that the invention is not to be limited to the disclosed embodiments, but on the
contrary, is intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims.
WE CLAIM
1. An apparatus for manufacturing high temperature superconducting (HTS)
coil, the apparatus comprising:
two side plates (14) disposed in facing relation;
a bobbin (12) disposed between the side plates, the bobbin receiving
layers of HTS tape (18) interposed with a binder; and
a plurality of blocks (16) assembled adjacent an outer edge of the side
plates, the blocks being displaceable toward the bobbin to compress the
layers of HTS tape on the bobbin.
2. An apparatus as claimed in claim 1, wherein the plurality of blocks (16)
are assembled on the outer edge of the side plates (14) via bolts.
3. An apparatus as claimed in claim 2, wherein the bolts are sized to
stepwise compress the layers of HTS tape (18).
4. An apparatus as claimed in claim 2, wherein the plurality of blocks (16)
comprise blocks of different thicknesses for selective compressing
according to a number of layers of the HTS tape (18).
5. An apparatus as claimed in claim 2, wherein the plurality of blocks (16)
comprise a plurality of final blocks that are shaped according to desired
outside dimensions of the superconducting coils.
6. An apparatus as claimed in claim 1, wherein the binder comprises prepreg
filament-ply interlayer insulation.
7. An apparatus as claimed in claim 1, wherein the binder comprises a
thermoplastic material.
8. An apparatus as claimed in claim 1, wherein the bobbin (12) is racetrack
shaped with substantially straight sides.
9. A method of manufacturing high temperature superconducting (HTS) coils
with an apparatus having two side plates (14) disposed in facing relation,
a bobbin (12) disposed between the side plates, and a plurality of blocks
(16) assembled adjacent an outer edge of the side plates, the blocks
being displaceable toward and away from the bobbin, the method
comprising
(a) winding HTS tape (18) onto the bobbin (12);
(b) applying a binder to the wound HTS tape (18);
(c) compressing the HTS tape and the binder against the bobbin (12)
with the plurality of blocks (16); and
(d) baking the compressed HTS tape and the binder to thereby cure
the binder.
10. A method as claimed in claim 9, wherein steps (a), (b) and (c) are
practiced for each layer of the HTS tape (18).
11. A method as claimed in claim 9, wherein steps (b) and (c) are practiced
after winding multiple layers of the HTS tape (18).
12. A method as claimed in claim 11, wherein step (b) is practiced by epoxy-
impregnating the wound multiple layers of the HTS tape (18) by a vacuum
pressure impregnation process.
13. A method as claimed in claim 11, wherein step (a) is practiced using HTS
tape (18) with a pre-preg coating.
14. A method as claimed in claim 9, comprising, prior to step (a), the step of
securing a start lead of the coil to a lead terminal on one of the two side
plates, and applying a binder layer to the bobbin (12).
15. A method as claimed in claim 14, comprising, prior to step (d), the step of
securing a finish lead of the coil to a lead terminal on the other of the two
side plates (14), applying a layer of copper foil to the coil with a
rectangular cooling heat exchanger tube bonded thereto, and repeating
step (c) under heat.
16.A method as claimed in claim 9, wherein the bobbin (12) is racetrack
shaped with substantially straight sides, and wherein step (c) is practiced
by compressing the HTS tape (18) and the binder against the straight
sides of the bobbin.
17. A method of manufacturing high temperature superconducting (HTS)
coils, the method comprising:
(a) winding HTS tape (18) onto a bobbin (12);
(b) applying a binder to the wound HTS tape;
(c) compressing the HTS tape and the binder; and
(d) baking the compressed HTS tape and the binder to thereby cure
the binder.

An apparatus for manufacturing high temperature superconducting (HTS) coil,
the apparatus comprising two side plates (14) disposed in facing relation; a
bobbin (12) disposed between the side plates, the bobbin receiving layers of HTS
tape (18) interposed with a binder; and a plurality of blocks (16) assembled
adjacent an outer edge of the side plates, the blocks being displaceable toward
the bobbin to compress the layers of HTS tape on the bobbin.