Claims:WE CLAIM:
1. A process to develop high strength fibre reinforced plastic composite tube (7), comprising the steps of:
holding a known composite tube (2) to a rotor sleeve on one end including a shaft on the other hand;said composite tube (2) is held by means of couple of stainless steel flanges (1 & 3) having grooves made on them, throughout their circumference;
inserting dowel pins (4 & 6) in said grooves throughout the circumference on said stainless steel flanges (1 & 3);
weldingsaid dowel pins (4 & 6) on the tapered surface of said stainless steel flanges (1 & 3) throughout their circumference to ensure high strength binding of fibre on a composite part (2);
said composite part (2) is asymmetric in nature and hence it is developed up to required thickness using the filament winding;
said composite part (2) is produced from continuous-fibre tows which are then further passed through an epoxy resin bath before being wound together to form saidhigh strength fibre reinforced plastic composite tube (7).

2. The process as claimed in claim 1, wherein the fibre used for developing said high strength fibre reinforced plastic composite tube (7) is Kevlar-49.

3. The process as claimed in claim 1, wherein the epoxy resin used for developing said high strength fibre reinforced plastic composite tube (7)is selected, but not limited to, from a group of low temperature application epoxy.

4. The process as claimed in claim 1, wherein said high strength fibre reinforced plastic composite tube (7) transfers the torque of 30 KN-m.

5. The process as claimed in claim 1, wherein said high strength fibre reinforced plastic composite tube (7) minimizes total heat loss to 45 W. , Description:FIELD OF THE INVENTION
[001] The present invention generally relates to the development of FRP (Fibre Reinforced Plastics) composite tube. More particularly, the present invention relates to the development of FRP (Fibre Reinforced Plastics) composite tube for HTS (High Temperature Superconducting) rotating machine.
BACKGROUND OF THE INVENTION
[002] The thermal and mechanical design of superconducting rotors for synchronous machines is different from the designs of rotors of conventional synchronous machines. The rotor part of superconducting motors contains HTS pole coils which are cooled by cryogenic fluid (at temperature of the order of 30 K). The cryogen is supplied to the rotor through cold medium transfer coupling system at the non-driven end. In order to maintain the cryogenic environment, the cryostat that supports and cools the HTS pole coils is insulated from the ambient temperature by means of a vacuum space. Two radial composite torque tubes connect the room temperature end shaft with the low temperature pole coil part. Therefore, the torque tube plays an important role in isolating heat and transferring torque between the warm parts and the cold parts. Torque tube must not only be strong and stiff but also should have very low thermal leakage for best performance.

[003] In US 7075208, to reduce the amount of heat which is introduced into the cooled superconductive area of the rotor, a torque transmitting hollow cylindrical composite body composed of a glass fibre-reinforced plastic is used.

[004] In US 5880547, torque tubes made of glass epoxy are secured between first and second ends of shafts located inside the rotor support for heat insulation.

[005] In US 6700274, torque tube is formed of a high strength and low thermal conductivity (e.g., Inconel718, Ti6A14V, or a composite material) and is positioned to support the rotor structure. The rotor assembly includes torque tube for transferring the rotational forces granted by the rotor assembly to a shaft via an endplate.

[006] In US 6489701, rotor assembly includes a torque tube for transferring the rotational forces of rotor assembly to shaft. Torque tube is formed of a high strength, low thermal conductivity composite material such as G-10 phenolic or woven glass epoxy.
[007] In all the above mentioned prior arts, none of the prior art teaches a composite tube which is made up of a very high strength and low thermal conducting Kevlar-49 material.
[008] The present invention is relates to a composite tube which is made up of a very high strength and low thermal conducting Kevlar-49 material.
OBJECTS OF THE INVENTION
[009] It is therefore an object of the present invention to develop an FRP composite torque tube for HTS machine using high strength Kevlar–49 fibre which facilitates transmission of high torque.
[0010] Another object of the present invention is to design and develop an FRP composite torque tube, for HTS machine, which has a maximum heat loss of 45 W when one end of the tube is maintained at the temperature of 30 K and the other end at 300 K.
SUMMARY OF THE INVENTION
[0011] A HTS motor has windings cooled by cryogenic fluid at temperature of the order of 30 K. The low temperature is mandatory to maintain the superconductivity. In order to maintain the cryogenic environment, the cryostat that supports and cools the HTS windings is insulated from the ambient by a vacuum space. Two radial composite torque tubes connect the room temperature shaft with the lower temperature HTS coil assembly rotor sleeve part. In order to improve the overall performance of HTS motor, a torque tube with high strength and low thermal leakage has been designed. Torque tube in HTS motor is used for supporting rotor, thermal isolation and high torque transmission.
[0012] The present invention relates to design of FRP composite torque tube which can transfer very high torques of the order of 30 KN-m while maintaining heat loss of about 45 W through it. Kevlar-49 fibre with suitable epoxy composite is chosen as the construction material for its high strength and low conductivity properties.
BRIEF DESCRIPTIONS OF THE ACCOMPANYING DRAWINGS
[0013] The above brief description, as well as further objects, features and advantages, of the present invention can be fully appreciated by reference to the following detailed description. These features of the present invention will become more apparent upon reference to the drawings, wherein:
Fig. 1: Cross sectional view of FRP torque tube according to the present invention
DETAIL DESCRIPTION OF THE INVENTION
[0014] The present invention will be described in detail below with reference to an embodiment as shown in the drawing.
[0015] In HTS motors, a high strength and low heat transmitting torque tube is used required to improve the overall efficiency of the motors. A torque tube connects the room temperature end shaft at 300 K with the low temperature HTS windings part at 30 K and acts as a heat insulator between the cold rotor part and the ambient temperature part. The entire torque tube component is under ultra high vacuum level of 10-6mbar.
[0016] Majority of the heat leak in the cold part is due to the heat conduction through the main rotor shaft of HTS motor. Hence, the torque tube which is employed should have a low thermal conductivity to minimize the heat invasion.
Ref. to Fig. 1, a composite tube (2) is held to the rotor sleeve (not shown) at 30 K on one end and held to the shaft (not shown) on the other handat room temperature by means of couple of interface stainless steel flanges (1 & 3). Certain grooves are made on the surface of the stainless steel flanges (1 & 3) and dowel pins (4 & 6, respectively) are inserted in the said grooves and are also welded on the tapered surface of the stainless steel flanges (1 & 3) throughout their circumference for additional safety.
[0017] The dowel pins (4 & 6) are provided to ensure high strength binding of fibre on composite part (2). The composite part (2) is developed for required thickness using filament winding technique due to the asymmetric nature of the tube (2). The asymmetric composite part (2) is produced from continuous-fibre tows which are then further passed through aepoxy resin bath before being wound together to form an fibre reinforced plastic tube (7).
[0018] The developed fibre reinforced plastic tube (7) can transfer torque of the order of 30 KN-m and minimize the total heat loss to maximum of 45 W.