FIELD OF THE INVENTION
The present invention relates to a rotor sleeve for superconducting pole coils of
convection cooled high temperature synchronous motor, which cools and maintain the
pole coils at optimum cryogenic temperature.
BACKGROUND OF THE INVENTION
A typical High Temperature Superconducting (HTS) machine with superconducting rotor
has superconducting coils in the rotor. These superconducting coils are used to create
electromagnetic poles, hence superconducting coils are sometimes referred to as pole
coils. These superconducting coils are cooled to required cryogenic temperatures with
the help of a cryocooler. If cryogen used is in the gas form, the cooling circuit becomes
a convective heat transfer type of cooling system and the pole coils are cooled with the
help of gaseous cryogen.
A cryocooler is used for achieving and sustaining desired cryogenic temperatures in HTS
machines. The cryocooling process is carried out in a closed loop process. In this
process, cold gas is transferred from cryocooler to HTS application while warm gas is
collected from HTS application and given back to cryocooler.
In the cooling circuit, the cold and warm gas must be contained in the pipings and
headers. These pipings and headers along with pole coil have to be rested over some
strong cylindrical sleeve. Since the cryogenic assembly is under vacuum, this sleeve
must not add gaseous molecules through degassing to vacuum and should not
deteriorate the vacuum of the HTS rotor. The torque is generated in the pole coils of
rotor of superconducting motor. Usually materials loose mechanical strength at

cryogenic temperatures, but this sleeve, on which pole coils are mounted, must not
loose its mechanical strength. It should safely transfer the torque to the load connected
at drive end of the motor.
1.Patent No. EP 913023B1 Title : Superconducting Synchronous Motor Construction
Abstract:
A rotor assembly for use within a superconducting electric motor includes a
superconducting winding formed of high temperature superconductor and during
operation, generates a flux path within the rotor assembly; and a high permeability
magnetic material, positioned within at least a portion of the flux path so as to decrease
the overall reluctance of the flux path. The rotor assembly may include a support
member having an internal volume and formed of non-magnetic, high-strength resilient
material. The support member supports on its outer surface the superconducting
winding and within its internal volume, the high permeability magnetic material. The
magnetic material may be in the form of a core member to provide the low reluctance
portion to the flux path generated by the superconducting winding.
2.Patent No. WO 0049703A9
Title: High Temperature Superconducting Rotor For A Synchronous Machine
Abstract:
A high temperature superconducting rotor for a synchronous machine includes a high
temperature superconducting field winding, a field winding support concentrically
arranged about the high temperature superconducting field winding, and a thermal
reserve concentrically arranged about the field winding support. The thermal reserve
includes a thermally conductive material. The material is either electrically conductive,

for example, aluminum , or electrically non-conductive, for example, ceramics such as
beryllium oxide or alumina. The thermal reserve material includes segmentation in a
direction normal to the rotor axis, along the rotor axis, neither, or both. The rotor
includes a banding concentrically arranged about the thermal reserve. The banding
includes an electrically conductive material, for example, steel, an electrically non-
conductive material, for example, Kevlar, or both. The rotor includes an outer layer
concentrically arranged about the thermal reserve. The outer layer includes a thermally
non-conductive material.
3. Patent No. EP 913023A1
Title: Superconducting Synchronous Motor Construction
Abstract:
A rotor assembly for use within a superconducting electric motor includes a
superconducting winding formed of high temperature superconductor and during
operation, generates a flux path within the rotor assembly; and a high permeability
magnetic material, positioned within at least a portion of the flux path so as to decrease
the overall reluctance to the flux path. The rotor assembly may include a support
member having an internal volume and formed of a non-magnetic, high-strength
resilient material. The support member supports on its outer surface the
superconducting winding and within its internal volume, the high permeability magnetic
material may be in the form of a core member to provide the reluctance portion of the
flux path generated by the superconducting winding.
4. Patent No. US 20120274161A1
Title : Rotor Core And Superconducting Rotating Machine With The Rotor Core.
Abstract:

Provided are a rotor core, a method for cooling a rotor core, and a superconducting
rotating machine, capable of effectively and uniformly cooling superconducting coils
without causing cold brittleness in an extremely low temperature . The rotor core,
which is made of substantially hollow cylindrical member of nonmagnetic material has a
cylindrical cavity defined therein and extending in the longitudinal axis of the member.
Helium gas is deliver4ed in the rotor core the proximal to distal sides and vice versa,
which ensures a uniform cooling of the rotor core. This also ensures a uniform and
effective cooling of the superconducting coils.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a Rotor Sleeve for superconducting
pole coils of convection cooled High Temperature Superconducting (HTS) synchronous
motor which contains the pole coils.
Another object of the invention is to propose a rotor sleeve for superconducting pole
coils of convection cooled high temperature synchronous motor, in which the rotor
sleeve is formed with a non-magnetic material to ensure that the signature of magnetic
field lines remains un-disturbed even a cryogenic temperatures.
A still another object of the invention is to propose a rotor sleeve for superconducting
pole coils of convection cooled high temperature synchronous motor, in which the Rotor
Sleeve to hold at least six numbers of superconducting pole coils each placed in a
housing along with associated cold and warm gas pipings including electrical and
instrumentation connections.

Yet another object of the invention is to proposea rotor sleeve for superconducting pole
coils of convection cooled high temperature synchronous motor, wherein the rotor
sleeve is configured to further hold two numbers of torque tubes both at drive and non-
drive ends.
Another object of the invention is to propose a rotor sleeve for superconducting pole
coils of convection cooled high temperature synchronous motor, in which the Rotor
Sleeve is formed to have optimum thermal mass along with mechanical strength
including torsional strength even at cryogenic temperatures.
A still another object of the invention is to propose a rotor sleeve for superconducting
pole coils of convection cooled high temperature synchronous motor, wherein the Rotor
Sleeve is enabled to safely transfer electromagnetic torque generated in the machine to
torque tubes and shafts and ultimately to load even at cryogenic temperatures.
Yet another object of the invention is to propose a rotor sleeve for superconducting
pole coils of convection cooled high temperature synchronous motor, wherein the Rotor
Sleeveis formed and assembled with minimum allowable ovality and eccentricity.
Further object of the invention is to propose a rotor sleeve for super conductingpole
coils of convection cooled high temperature synchronous motor, in which the Rotor
Sleeve is formed from material having inherently low degassing characteristic under
high vacuum of the order of 10-6 mbar.
Still further object of the invention is to propose a rotor sleeve for super conducting
pole coils of convection cooled high temperature synchronous motor wherein the rotor
is assembled with the superconducting pole coils to ensure avoidance of any electrical
short and that the complete assembly offer high insulation resistance.

SUMMARY OF THE INVENTION
Accordingly, there is provided a rotor sleeve for super conducting pole coils of
convection cooled high temperature synchronous motor comprising a rotor Sleeve; a
plurality of tapped holes on each side of the rotor sleeve for fastening Drive End and
Non Drive End torque tubes; a plurality of Counter bore holes provided on the rotor
sleeve for fastening at least six numbers of superconducting pole coils having housing
wherein said at least six numbers of superconducting pole coils each placed in the
housings and fastened onto the housings along with their associated cold and warm gas
pipings including electrical and instrumentation connectionswherein two numbers of
torque tubes on both drive and non-derive ends of the rotor sleeve fastened on each
side and wherein the poles with housing are assembled with minimum allowable ovality
and eccentricity.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 Longitudinal Cross Section of Rotor Sleeve for HTS Pole Coil Housings.
Fig. 2 Sectional View of Rotor Sleeve for HTS Pole Coil Housings.
Fig. 3 Sectional View vis-à-vis Longitudinal Cross Section of Rotor Sleeve
Fig. 4 Cross Sectional View of Rotor Sleeve along with HTS Pole Coil Housings.
Fig. 5 Longitudinal Cross Section of Rotor Sleeve along with HTS Pole Coil.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Figure 1 represents longitudinal cross section of Rotor Sleeve 101 for HTS pole coil
housings for a convection cooled HTS machine rotor. The rotor sleeve has provision for
fastening pole coil housing on suitable number of counter bores 102. The suitable

number of tapped holes 103, 104 are provided on each side of rotor sleeve for
fastening Drive End and Non Drive End Torque tubes.
Figure 2 represents sectional view of Rotor Sleeve 201 for HTS pole coil housings for a
convection cooled HTS machine rotor. The rotor sleeve has provision for fastening pole
coil housing from inside on suitable number of counter bores 202. These housings
contain superconducting pole coils which are to be kept at cryogenic temperatures
during the operation. The suitable number of tapped holes 203 are provided on each
side of the rotor sleeve for fastening Drive End and Non Drive End torque tubes. These
torque tubes transfer mechanical torque to shafts and at last to loads.
Figure 3 represents sectional view vis-à-vis longitudinal cross section of Rotor Sleeve
301, 305 for HTS pole coil housings for a convection cooled HTS machine rotor. Rotor
sleeve has provision as suitable number of counter bores 302, 306 for fastening pole
coil housings from inside. The number of pole coils are usually in even numbers for a
synchronous machine. The suitable number of tapped holes 303, 304, 307 are provided
on each side of rotor sleeve for fastening Drive End and Non Drive End torque tubes.
These torque tubes are made of insulating material to minimize heat loads of HTS
machine.
Figure 4 represents sectional view of rotor sleeve 402 along with six HTS pole coil
housings 401 for a convection cooled HTS machine rotor. For a multi-pole synchronous
superconductingmachine, there can be more than one pole pair. One pole pair consists
of two superconducting pole coils. The pole coil housings are fastened on top by placing
the pole housings inside the rotor sleeve. The suitable number of tapped holes 403 are
provided on each side of rotor sleeve for fastening Drive End and Non Drive End torque
tubes.

Figure 5 represents longitudinal cross section of Rotor Sleeve 501 along with HTS pole
coil housing 506 for a convection cooled HTS machine rotor. The drawing pertains to a
six pole machine containing six superconducting pole coils which are individually housed
in six housings. The present longitudinal cross section shows two such housings, one at
top and other one at bottom. The top lid of HTS pole coil housings is bolted to bottom
one and hence, completes the assembly of individual superconducting pole coil 507.
The pole coil housings are fastened on top by placing the pole coil housings inside the
rotor sleeve. The suitable number of tapped holes 503, 504 are provided on each side
of rotor sleeve for fastening Drive End and Non Drive End torque tubes. The housing of
each superconducting pole coil has one cold gas inlet port 508, one warm gas outlet
port 509 and two ports 510 for electrical and instrumental connections.

WE CLAIM :
1. A rotor sleeve for superconducting pole coils of convection cooled high
temperature synchronous motor, comprising :
a) a rotor sleeve (101);
b) a plurality of tapped holes (103, 104) on each side of the rotor sleeve (101)
for fastening drive End and Non Drive End torque tubes;
c) a plurality of Counter bore holes (102) provided on the rotor sleeve (101) for
fastening at least six numbers of superconducting pole coils (507) having
housing wherein said at least six numbers of superconducting pole coils (507)
each placed in the housings and fastened onto the housings along with their
associated cold and warm gas pipings including electrical and instrumentation
connections, wherein two numbers of torque tubes on both drive and non-
drive ends of the rotor sleeve (101) fastened on each side and wherein the
poles with housing are assembled to the rotor sleeve (101) with minimum
allowable ovality and eccentricity.

2. The rotor sleeve as claimed in claim 1, wherein the rotor sleeve (101) is made of
non-magnetic material to maintain the original signature of magnetic field lines
even at cryogenic temperatures.
3. The Rotor sleeve as claimed in claim 1, wherein the rotor sleeve (101) is
constructed to have strength for safe transfer of electromagnetic torque
generated in the machine to the torque tubes and shafts and ultimately to load
even at cryogenic temperatures.

4. The Rotor Sleeve as claimed in claim 1, wherein the rotor sleeve assembly (101,
507) maintains high vacuum of the order of 10-6 mbar without considerable
change in vacuum due to degassing of the rotor sleeve.
5. The Rotor Sleeve as claimed in claim 1, wherein the rotor sleeve (101) maintains
high insulation resistance in the complete assembly.