FIELD OF INVENTION
Present invention relates to detachable vacuum chamber for high temperature superconducting (HTSC) rotary assembly of rotating machines like motor/generators. More particularly, the invention relates to detachable type vacuum chamber for enabling maintenance and repair of several important items mounted inside the vacuum chamber.
BACKGROUND OF THE INVENTION AND PRIOR ART
The field coils of HTSC rotating machines are made with high temperature superconducting (HTSC) tape. These field coils are accommodated in rotating vessels called as housings. The vessels are mounted on a rotating sleeve, which is covered by a vacuum enclosure. This makes a rotating cryostat. The operating temperature of the field coils made with HTSC tape is below 30K. In order to cool the HTSC field coils of the machine, a cold gas flows from a cryocooler to the rotating cryostat. The low speed HTSC machines are usually a multi-pole machines having more than one pole pair. There is a possibility of large amount of heat in-leak owing to high temperature difference between atmosphere and cryogenic zone of a HTSC rotating machine in absence of proper insulation system. The quantity of heat in-leak can be reduced by reducing heat transfer via conduction, convection and radiation. The above invention enables easy access to HTSC components inside the vacuum chamber and offers easy

maintenance of the system for several times. The gas distribution system, field coil housing, torque tubes and few other components are inside the vacuum chamber. This invention also eliminate the convective heat transfer from atmosphere to cryogenic zone of HTSC rotating machine.
The typical operating temperature of the 1st generation HTSC conductor is 25-40K and for the 2nd generation conductor it is still higher, probably in the range of 50-65K but certainly lower than the liquid nitrogen temperature i.e. ~ 77K. For an HTSC machine, there is enormous amount of heat load because of difference between room temperature and operating temperature of field coils of HTSC machine in absence of a proper insulation system. This heat load is due to radiation, solid/gas conduction and fluid convection from adjacent regions or structures.
There are three modes of heat transfer- conduction, convection and radiation. The HTSC rotating machines operate at a temperature much below than atmospheric temperature, so heat transfer is always associated with such systems. Hence, it is main concern to reduce the heat transfer rate to a very low value for HTSC machines. This is done by using a good insulation system. There are several types of insulation system which is used for cryogenic application, and vacuum insulation is one of them. The vacuum insulation alone is used in several cryogenic application because it eliminates two components of heat transfer- solid conduction and gaseous convection. This arises

the requirement of a vacuum chamber for HTSC rotating machines like motor/generator.
A typical HTSC rotating machine consists many sub-components as described in figure 1. Prior to this invention the component called vacuum chamber was welded at two end shafts, which makes it a permanent joint. Any required modification inside the vacuum chamber related with instrumentation and gas distribution system, it was required to de-weld at both ends to get access to the components which is inside the vacuum chamber. This procedure reduces the length of vacuum chamber in each modification, and further modification cannot be done because the length of vacuum chamber will become short for reuse. The elimination of this great disadvantages of prior Art required an inventive idea for a solution to the problem.
PRIOR ART
WO1992021175A1: The present invention relates to novel magnet-superconductor systems, and to bearings and other articles utilizing magnet-superconductor systems. In another aspect the present invention relates to magnet-superconductor systems having high thrust and high stability and to a method for increasing the thrust and stability of magnet-superconductor systems.
JP2001244109A: The present invention relates to provide a high-temperature superconducting coil device which slowly restricts heat generated from a coil conductor,

etc. In a high-temperature superconducting coil device, a heat transmission plate is inserted into an intermediate part between superconducting coils and formed in a layered manner, a heat-absorbing body is mounted on a front layer surface of the superconducting coils, and the heat transmission plate and heat-absorbing body are connected to a freezer via heat transfer bodies.
US 7667358 B2: In this patent Inventors described cooling structure of a superconducting motor in which a superconducting coil is attached to a rotor, grooves are concavely provided on an outer surface of a rotating shaft that penetrates and is fixed to the rotor. A refrigerant is circulated through a refrigerant circulation pipe disposed inside the grooves to that the superconducting coil is cooled by the refrigerant.
US20120274161A1: This patent relates to the structure of the
superconducting rotor core. In this method, superconducting field coils are mounted on rotor core. The rotor core is made of a heavy solid member. The rotor core comprises rod like members and each coaxially disposed in the cryogen passage for effective cooling of field coils.
US20140217850A1: In this invention the superconducting coils are mounted with yoke and bobbin with fiber connection type arrangement for avoiding conducting

type heat in leak. Inventor used this method for better cooling effect to superconducting coils which is achieved with low heat in leak through conduction.
OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose a detachable vacuum chamber for high temperature superconducting (HTSC) rotary assembly of rotating machines, which is capable of providing an easy means to detach the chamber and perform the maintenance or repairing of important items inside the chamber.
Another object of the invention is to propose a detachable vacuum chamber for high temperature superconducting (HTSC) rotary assembly of rotating machine, which is able to reduce external heat in-leak to cryogenic zone of a HTSC machine.
A further object of the invention is to propose a detachable vacuum chamber for high temperature superconducting (HTSC) rotary assembly of rotating machine, which can provide effective cooling of superconducting field coils by maintaining high level of vacuum envelop around field coil housing of the HTSC machine.
A still further object of the invention is to propose a detachable vacuum chamber for high temperature superconducting (HTSC) rotary assembly of rotating machine,

which is capable of providing required mechanical strength to the flexible or detachable joint.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1: Shows a sectional view of rotor of a HTSC rotating machine.
Fig. 2: Shows a sectional view of drive end shaft.
Fig. 3: shows a sectional view of non-drive end shaft.
Fig.4: Shows a sectional view of vacuum chamber.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
Fig 1 represents the schematic diagram of the HTSC rotor assembly. The HTSC rotor assembly mainly consist rotor sleeve (106), HTSC coil assembly (105), two torque tubes (103 & 104), radiation shield (102), vacuum chamber (101) and two end shafts (107 & 108). The HTSC coil assembly (105) is mounted on inner periphery of rotor sleeve (106). This sleeve (106) is supported on two torque tube (103 & 104) at both sides. These torque tubes (103 & 104) are further integrated with both side end shafts (107 & 108). The function of torque tubes (103 & 104) is to minimize the conduction heat in-leak to the HTSC coil assembly. A radiation shield (102) is mounted over the HTSC coil assembly (105) to minimize the radiation heat in-leak. These components are

encapsulated in a vacuum chamber (101). The function of vacuum chamber (101) is to maintain a high level of vacuum inside to eliminated the convective heat in-leak to the HTSC pole coil assembly (105). The radial O-ring (109) and face seal O-ring (110) provide sealing on NDE side and similarly radial O-ring (111) and face seal O-ring (112) provide sealing on DE side. These O-rings does not allow atmospheric to enter in side vacuum chamber and thus maintains high vacuum.
Fig 2 represents the sectional view of drive end shaft. The main function of drive end shaft is to transmit the torque developed in machine to end application. Here, the drive end shaft is also used to hold the vacuum chamber. The drive end shaft (108) has an extended flange (201), which is having a drilled hole (202). The vacuum chamber flange gets bolted with the extended flange (201) of drive end shaft and rigidly jointed with the bolts. It compresses the O-ring (111) kept in groove (203). The compressed O-ring provide a leak tight joint which does not allow to enter any gas from outside to vacuum chamber. The shaft extension (205) is for bearing and other requirements.
Fig 3 represents the sectional view non drive end shaft. This shaft also take part in torque transmission like drive end shaft and also to hold rigidly the vacuum chamber. But unlike the drive end shaft, the non-drive end shaft does not have the extended flange. The vacuum chamber flange gets bolted with threaded hole (302) in non-drive end shaft. One radial groove (301) is provided sealing on outer periphery of non-drive end shaft flange. This O-ring gets pressed when vacuum chamber slides over the shaft

and thus provide leak tight joint. The torque tube is also hold rigidly with the non-drive end shaft by tapped hole (303). The shaft extension (304) is for bearing mounting and other requirement.
Fig 4 represents the sectional view of vacuum chamber. The vacuum chamber works like an outer envelope to HTSC rotor assembly consisting rotor sleeve and torque tubes along with radiation shield. The two way of heat in-leak i.e. conduction and radiation were already reduced by using torque tube and radiation shield. But the convective heat in-leak is eliminated by creating ultra-high vacuum inside vacuum chamber by pumping out all the gasses from chamber. The vacuum chamber has a cylindrical part (401), two flanges on each side. One side of flange is protruded radially outer side and in other side the flange is made radially inner side. It is made so to ease in assembly as well as due to less air gap. The O-rings are placed in the grooves (404 & 405) for making it leak proof and it does not allow any gas to enter in vacuum chamber when it is evacuated and ultra-high vacuum is maintained. The flanges are fixed at both end by drive and non-drive end shafts rigidly at (402 & 403).
ADVANTAGES OVER THE PRIOR ART
1. Easy access inside the vacuum chamber to carry out any modifications/changes.
2. Reduction of external heat in-leak to cryogenic zone of a HTSC machine.
3. Effective cooling of superconducting field coils.
4. Ultra-high vacuum is maintained inside vacuum chamber.

5. Easy maintenance / repair of gas distribution system, field coil housing, torque tubes and other components, which are mounted inside vacuum chamber.
6. Significant mechanical strength to the flexible or detachable joint of vacuum chamber.
REFERENCE NUMERALS USED IN THE DRAWINGS
101 - Vacuum chamber
102 - Radiation shield
103 - Torque tube at drive end side
104 - Torque tube at non-drive end side
105 - HTSC coil assembly
106 - Rotor sleeve
107 - Non-drive end (NDE) shaft
108 - Drive end (DE) shaft
109 - Radial O-ring on NDE side
110 - Face seal O-ring on NDE side
111 - Radial O-ring on DE side
112 - Face seal O-ring on DE side

201 - Shaft flange
202 - Hole for fixing the chamber with drive end shaft
203 - Groove for sealing
204 - Tapped hole for fixing torque tube

205 - Shaft extension
301 - Groove for sealing
302 - Tapped hole for fixing vacuum chamber flange
303 - Tapped hole for fixing torque tube
304 - Shaft extension

401 - Cylindrical part of vacuum chamber
402 - Hole for fixing with drive end shaft flange
403 - Hole for fixing with non-drive end shaft flange
404 - Groove for sealing at non drive end side
405 - Groove for sealing at drive end side

WE CLAIM
1. A detachable vacuum chamber (101) for a high temperature superconducting
(HTSC) rotary assembly of rotating machines, the said detachable vacuum chamber (101) comprising;
a cylindrical part (401) with two flanges (406, 407) on each side configured integrally with the said cylindrical part, one side of flange (406) protruded radially outer side and other side flange (407) protruded radially inner side for fecilitating assembly with non-drive end (107) and drive end (108) shaft on two sides of said chamber (101), the said chamber bolted to an extended flange (201) of drive end shaft (108) and to non-drive end shaft;
the HTSC rotor assembly with rotor sleeve (106), a HTSC coil assembly (105) mounted on inner periphery of rotor sleeve (106), two torque tubes (103, 104) supporting the sleeve (106) and integrated with both side end shafts (107, 108), a radiation shield (102) mounted over HTSC coil assembly, the said components disposed in the detachable vacuum chamber,
radial O-ring (109) and face seal O-ring (110) disposed in grooves (301) of non-drive end shaft;
radial O-ring (111) and face seal O-ring (112) disposed in the grooves (203) of drive end shaft for providing leak tight joint of non-drive end and drive-end flanges with detachable vacuum chamber (101);
Characterized in that,

the detachable vacuum chamber (101) is disposed in the system for eliminating the convective heat in-leak to HTSC pole coil assembly by maintaining a high level of vacuum inside and for providing easy access for maintenance of HTSC components inside the vacuum chamber and is configured with radial (109, 111) and face seal (110, 112) O-rings pressed inside the grooves (303, 203, 404, 405) for providing leak tight joint restricting any gas to enter from outside to vacuum chamber (101).