FIELD OF THE INVENTION
The present invention relates to a cryogen Exchanging device for coaxial transfer lines
of high temperature super conducting synchronous machine rotor.
BACKGROUND OF THE INVENTION
A cryocooler is used for achieving and sustaining desired cryogenic temperatures in HTS
machines. The cryocooling operation 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. Cryocooler has a vacuum
jacketed line for transfer and collection of cryogen along with flexibility of mechanical
connections. Usually the vacuum jacketed lines is connected to a cryogen exchanging
device of HTS machine. This cryogen exchanging device connects the stationary
cryocooler and the rotating superconducting rotor of the HTS machine.
The design of a cryogen exchanging device for coaxial transfer lines of high
temperature superconducting synchronous machine rotor, is based on certain
parameters namely, minimum helium leak rate during stationary as well as rotating
condition, minimum heat in leak from atmosphere, no heat and mass transfer between
in-going cold and out-coming warm cryogen, containment of basic characteristics of
materials employed in cryogen exchanging device for primary seal unit and secondary
seal unit for multiple cycle of room temperature to cryogenic temperature in stationary
as well as rotating conditions, minimum ovality and eccentricity during assembly, non-
freezing conditions near O-rings and bearings etc.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a cryogen exchanging device for
coaxial transfer lines of high temperature superconducting synchronous machine rotor.

Another object of the invention is to propose a cryogen Exchanging device for coaxial
transfer lines of high temperature super conducting synchronous machine rotor, which
achieves minimum helium leak rate (better than 10-6 mbar-litre/sec) through the
cryogen exchanging device.
A still another object of the invention is to propose a cryogen Exchanging device for
coaxial transfer lines of high temperature super conducting synchronous machine rotor,
which maintains mechanical integrity of the device including minimum permissible
helium leak rate during stationary condition.
Yet another object of the invention is to propose a cryogen Exchanging device for
coaxial transfer lines of high temperature super conducting synchronous machine rotor,
which maintains mechanical integrity of the device including minimum permissible
helium leak rate during rotating condition.
Another object of the invention is to propose a cryogen Exchanging device for coaxial
transfer lines of high temperature super conducting synchronous machine rotor, which
ensures minimum heat in leak from atmosphere to the device.
A still another object of the invention is to propose a cryogen Exchanging device for
coaxial transfer lines of high temperature super conducting synchronous machine rotor,
which ensures no heat and mass transfer between ingoing cold and out-coming warm
cryogen in the device.
Yet another object of the invention is to propose a cryogen Exchanging device for
coaxial transfer lines of high temperature super conducting synchronous machine rotor,
which maintains the basic characteristics of materials for primary seal unit and
secondary seal unit intact for multiple cycles of room temperature to cryogenic
temperature in stationary as well as rotating conditions.

Another object of the invention is to propose a cryogen Exchanging device for coaxial
transfer lines of high temperature super conducting synchronous machine rotor, which
ensures minimum permissible ovality and eccentricity while assembling cryogen
exchanging device.
A still another object of the invention is to propose a cryogen Exchanging device for
coaxial transfer lines of high temperature super conducting synchronous machine rotor,
which allows assembly of the cryogen exchanging device on a firm base with minimum
permissible vibrations.
Yet another object of the invention is to propose a cryogen Exchanging device for
coaxial transfer lines of high temperature super conducting synchronous machine rotor,
which attains the non-freezing conditions near O-rings so that the ‘O’ rings allows to
maintain vacuum tightness of intended spaces of the device.
A further object of the invention is to propose a cryogen Exchanging device for coaxial
transfer lines of high temperature super conducting synchronous machine rotor, which
ensures achieving non-freezing conditions at the lubricating bearings of the device so
that the lubrication of bearings does not freeze.
A still further object of the invention is to propose a cryogen Exchanging device for
coaxial transfer lines of high temperature super conducting synchronous machine rotor,
which maintains vacuum of magnitude 10-6 mbar in the intended spaces within the
device.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 – Primary Seal Unit of the Cryogen Exchanging Device of the invention.
Figure 2 – Secondary Seal Unit of the Cryogen Exchanging Device of the invention.
Figure 3 – Collection Chamber along with Coaxial Transfer Line Arrangement in the
Cryogen Exchanging Device of the invention.

Figure 4 – Bearing Housing and Shaft Assembly of Cryogen Exchanging Device of the
invention.
Figure 5 – Complete Assembly of the Cryogen Exchanging Device of the invention with
Primary and Secondary Seal unit.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Figure 1represents a Primary Seal Unit 101 for a Cryogen Exchanging Device to be
placed in the bearing housing (304) over the main shaft . This seal (101) works at just
above atmospheric pressure. The main cryogen pressure is reduced to just above
atmospheric pressure by a secondary seal unit (201).
Figure 2 represents the Secondary Seal Unit 201 for the Cryogen Exchanging Device to
be placed in a collection chamber. The main cryogen pressure is reduced to just above
atmospheric pressure by this seal unit (201).
Figure 3 represents a Collection Chamber along with Coaxial Transfer Line arrangement
in the Cryogen Exchanging Device. The Collection Chamber comprises one each cold
and warm gas connections 301, 302, a vacuum space 303 in pipings, a flange for
connecting intermediate chamber 304, a warm gas collection chamber sleeve 305, a
flange for connecting the bearing housing 306, a space (307) for placement of the
(201), and secondary seal (201), secondary seal unit 308and warm gas collection
chamber 309. Since the cryocooling operation of a superconducting machine is in a
closed loop, there is a need to transfer cold gas from the cryocooler to machine rotor
and to collect back warm gas from machine and send it back to the cryocooler. The cold
gas connection and warm gas connection 301, 302 of the Cryogen Exchanging Device
are made with respective cryocooler connections. Since cold as well as warm gas pipes
both are at cryogenic temperatures, both are separated from each other as well as from
room temperature surroundings through vacuum enclosures. Return warm gas is
collected in said collection chamber 510 and sent back to the cryocooler. The probability

of leakage of return gas through the bearings is reduced by decreasing pressure of
return gas by the secondary seal unit 501. The Bearing housing primarily contains a
main shaft 513 over which said bearings are placed. A shaft flange 512 connects the
Cryogen Exchanging Device to the machine. A bearing stopper 515 with the help of a
bearing spacer sleeve 517 contains a plurality of bearings 516 in place. O rings 521 and
groove 520 are provided to contain vacuum in intended places of the complete
assembly. A flange 519 connects the bearing housing to the collection chamber of the
device. Cold and warm gas pipings are arranged coaxially and are separated from each
other through a vacuum. The primary seal unit seals the final warm gas leaking after
the secondary seal unit. The cryogen flow path is shown with arrows along with coaxial
vacuum spaces. A port for monitoring the return helium gas 522 pressure is provided
after the secondary seal unit.

WE CLAIM :
1. A cryogen Exchanging device for coaxial transfer lines of high temperature super
conducting synchronous machine rotor, the device comprising :
a) a primary seal unit;
b) a secondary seal unit;
c) a warm gas collection chamber assembly;
d) a bearing housing assembly; and
e) a coaxial cryogen transfer lines separated by a created vacuum;
wherein a plurality of bearings are placed in said bearing housing assembly along
with the primary seal unit,
wherein the warm gas collection chamber is assembled along with said
secondary seal unit, and
wherein at least one each cold and warm gas connections are provided to both
sides of the cryocooler and the HTS machine.
2. The cryogen exchanging device as claimed in claim 1, which is configured to
maintain a helium leak rate better than 10-6 mbar-litre/sec.
3. The cryogen exchanging device as claimed in claim 2, wherein the device is
enabled to maintain the vacuum of magnitude of at least 10-6 mbar in the int-
ended spaces of the cryogen exchanging device.
4. The cryogen exchanging device as claimed in claim 3, wherein the device is
configured to allow a minimum heat leak from atmosphere to the vacuum
bifurcation chamber, and wherein changes in the temperature of cold and warm

gaspipings before and after cryogen exchanging device, is maintained
substantially constant.
5. The cryogen exchanging device as claimed in claim 1, wherein the device is
configured to maintain absolute mechanical integrity with minimum permissible
helium leak rate during stationary as well as rotating condition.
6. The cryogen exchanging device as claimed in claim 1, wherein the device
restricts any heat and mass transfer between in-going cold and out-coming
warm cryogen.
7. The cryogen exchanging device as claimed in claim 1, wherein the device is
constructed to maintain absolute mechanical integrity without allowing to
generate any ovality or eccentricity, and wherein the device is enabled to
develop minimum permissible vibrations on a firm base of the device during
rotating condition.
8. The cryogen exchanging device as claimed in claim 7, wherein the device is
constructed to maintain non-freezing conditions at said plurality of bearings as
well as at the O-rings during stationary as well as rotating condition.