FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF INVENTION
Winding assembly with cooled superconductor tapes having localised inter-turn insulation
APPLICANT(S)
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR (S)
Kedia Sunil, Dixit Manglesh, Kulkarni Sandeep, Sukali Ramesh all of Crompton Greaves Ltd, Global R&D Centre, Medium Voltage Product Technology Center, Kanjurmarg (E), Mumbai - 400042, Maharashtra, India; Lobo Anthony Marcel of Crompton Greaves Ltd, Global R&D Centre, High Voltage Product Technology Centre, Kanjurmarg (E), Mumbai - 400042, Maharashtra, India and Bharnuke Anirudha Keshav of Crompton Greaves Ltd, Global R&D Centre, Speciality Product Cell, Kanjurmarg (E), Mumbai - 400042, Maharashtra, India; all Indian Nationals
PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
This invention relates to the field of electro-mechanical equipment and mechanical and electrical engineering.
Particularly, this invention relates to winding structure for a superconducting winding for efficient cooling of the superconductor.
Specifically, this invention relates to Winding assembly with cooled superconductor tapes having localised inter-turn insulation.
BACKGROUND OF THE INVENTION
Many industrial sectors and power industries are now trying to efficiently use superconductor tapes for making equipment such as transformers, motors, alternators, fault current limiters, and the like. However, so far, most of these practical prototypes are operated at under-rated currents because of inadequate cooling. In some of the incidents, the superconductor based winding pack "quenches", and does not recover because of inadequate cooling and the product / equipment fails. Moreover, many of these practical systems / products / equipment require a number of parallel wound coils to increase the overall current carrying capability of the product, which hinders the cooling mechanism further. Thus, in order to get the desired level of current, more number of discs is being made.
Another issue with the present system is the thermal stress which is generated due to the cool down of the winding pack. Since compactness is desired in all these products / equipment, thermal stresses are generally neglected. But the current carrying capability of the superconductor reduces under stressed condition thereby

leading to failure.
Superconductor tapes are widely used for demonstrating increased efficiency in power products / equipment such as fault current limiters, transformers, motors etc. Because of its high current carrying capabilities and current limiting behavior (in certain scenarios), devices employing superconductors are more efficient and compact. However, winding of superconducting tape in coil shape becomes critical owing to the fact that the minimum bending radius is to be maintained and inter-turn insulation must allow good heat transfer from the coil to the surrounding coolant (generally liquid nitrogen or liquid helium). Because of the inherent properties of almost all insulating materials, the degraded thermal heat transfer between the coil and the coolant restricts proper cooling of the superconductor. Hence, if a normal zone is initiated due to any unforeseen scenarios or during fault operation of the superconducting fault current limiters; recovery of the superconductor winding to its superconducting state becomes difficult.
Most of the practical and prototype devices employing high temperature superconductors are in coil shape. In all these cases, inter-turn or / and inter-layer insulation is used in order to avoid the voltage breakdown. This compact winding scheme does not allow the coolant to penetrate through the winding pack even in bath cooled setups where the winding is immersed in the coolant (liquid nitrogen, liquid helium). Moreover, the surrounding insulation layer acts as a thermal insulator too. Hence, in any unforeseen fast events where the winding pack quenches, its recovery becomes difficult because of the deficiency of the cooling power. The heat diffusivity through the insulation into the cryogen in fast transient is very slow and hence the winding fails or burns.
The cooling becomes a major issue in cases where the superconductor is operated

with AC. More refrigeration power is required in case of AC operations, because of the finite AC losses in the superconductors, which is practically about 20-80 times of the heat load in DC condition. AC applications which demands the winding pack to quench (intentionally), such as superconducting fault current limiters, requires a very active heat transfer from the superconductor to the coolant (within 20-80 ms). Any winding geometry with insulating layer, thus fails to recover from the fault. Hence, the fault current limiters are designed for under rated operations thereby restricting the limiting effect. Better cooling can add to the performance of these devices.
Moreover, the thermal contraction of these compact winding geometries adds finite thermal strain to the conductor. Multi-windings add further to the electromagnetic strain because of the increased Hoop stresses due to multiplied current per turn. Hence, the superconductor remains in strained state and its critical current decreases. Thus, the winding geometry under-performs.
Winding a superconducting tape for AC power application is a challenging task and brings out a number of problems. One of the major problem being the adequate cooling of the superconductors in wound configuration. Multi winding of the superconducting tape adds to the cooling complexity of the problem. Moreover, as the current increases for the same winding geometry in multi-winding, the electromagnetic and thermal stress becomes a dominating factor in reducing the critical current of the winding pack. There is a need for a superconducting tape system in which both the major issues are addressed.
OBJECTS OF THE INVENTION
An object of the invention is to efficiently cool a multi-superconductor winding.

Another object of the invention is to provide a winding assembly such that it efficiently cools the winding during normal and quench cases.
Still another object of the invention is to provide flexibility to winding, of a winding assembly, during contraction and expansion due to temperature or electromagnetic forces.
An additional object of the invention is to provide the required insulation strength by maintaining maximum conductor area in direct contact with the coolant between turns of the winding, of a winding assembly, by introducing insulting rods of required diameters between the turns.
Yet an additional object of the invention is to make a device compact with reduced number of parallel discs by winding multiple superconductor tapes co-wound together.
Another additional object of the invention is to reduce the number of parallel windings required in certain applications such as in fault current limiters.
Yet another additional object of the invention is to reduce the number of turns by an order of 'n' in certain applications such as in superconducting magnets due to increased overall current density.
SUMMARY OF THE INVENTION
According to this invention, there is provided a winding assembly with cooled superconductor tapes having localised inter-turn insulation, said winding assembly comprises:

a. one or two or more superconductor tapes being wound together over a
bobbin in order to enhance the current carrying capacity per turn, said tapes
being helical coils;
b. plurality of sets of rods, each set being formed by rods located adjacent each
other, longitudinally, number of adjacent rods corresponding to gaps
provisioned by turns of said tapes, said plurality of sets of rods being
radially dispersed about the wound superconducting tape(s);
c. first side plate and a second side plate adapted to cover said bobbin wound
superconducting tapes from an operative distal direction and an operative
proximal direction, correspondingly; and
d. slots being provided on said first side plates in a corresponding said radially
dispersed manner about a central axis, each of said slots being relatively
longer than the set of rods.
Typically, said rods are insulating rods.
Typically, said second side plate comprises blind slotted grooves in order to arrest the movement of said rods in their longitudinal direction.
Typically, said bobbin is co-axial with said side-plates which form the upper and lower cover of said bobbin wound superconducting tapes.
Typically, said rods are made from a material selected from a group of materials consisting of Nylon, FRP, Teflon, or Mica tube.
Typically, said gap between each turn is a pre-defined gap adapted to be considered as per standard insulation of air gap to ensure that no voltage

breakdown occurs between inter turns.
Typically, said assembly comprises peripheral holes in said first side plate as well as in said second side plate in a matching manner such that said plates with superconducting tapes may be stacked in a non-inductive fashion; i.e. spaced apart from adjacent such assemblies of plates and superconducting tapes.
Typically, said one or more superconducting tapes are superconducting tapes which are wound together, in a parallel fashion, over a bobbin.
Alternatively, said one or more superconducting tapes are superconducting tapes which are wound together, in an anti-parallel fashion, over a bobbin.
Alternatively, said one or more superconducting tapes are superconducting tapes such that field direction of adjacent tapes are opposite.
Preferably, said rods are equi-spaced rods with a gap required as per the standard voltage clearance.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention will now be described in relation to the accompanying drawings, in which:
Figure 1 illustrates an exploded view of winding assembly with cooled superconductor tapes having inter-turn insulation;
Figure 2 illustrates a schematic isometric view of winding assembly with cooled

superconductor tapes having inter-turn insulation;
Figure 3 illustrates a schematic side view of winding assembly with cooled superconductor tapes having inter-turn insulation, in its non-inductive placed manner; and
Figure 4 illustrates a process of winding in a cryostat.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
According to this invention, there is provided winding assembly with cooled superconductor tapes having localised inter-turn insulation.
Figure 1 illustrates an exploded view of winding assembly with cooled superconductor tapes having inter-turn insulation.
Figure 2 illustrates a schematic isometric view of winding assembly with cooled superconductor tapes having inter-turn insulation.
Figure 3 illustrates a schematic side view of winding assembly with cooled superconductor tapes having inter-turn insulation, in its non-inductive placed manner.
In accordance with an embodiment of this invention, one or more superconductor tapes (4) are wound together in parallel over a bobbin (1) to enhance the current carrying capacity per turn. The superconductor tapes, typically, are helical coils. Inter-turn continuous insulation material, such as polyamide tape, of the prior art, is replaced by providing adequate gap between the consecutive turns in the

winding. Through these gaps, liquid coolant can penetrate and cool the superconductor tapes.
The aspect of winding two or more tapes (4) together in a multi winding configuration is performed such that the total current carrying capability of the coil would increase and the system using these superconducting tapes configuration (which may be superconducting magnet or any other power device) would be compact.
Typically, the bobbin (1) is co-axial with the side-plates (2, 3) which form the upper and lower cover of the superconducting tapes (4).
In accordance with another embodiment of this invention, the gap is maintained by inserting number of rods (5), between the turns of the winding that extends from top to bottom of the winding. Typically, a plurality of rods are placed adjacent each other in a radially dispersed fashion about the superconducting tape(s) (4). The rods may be Nylon / FRP / Teflon/Mica tube or rods. Generally, the insulating material used in the windings are of low thermal conducting materials and restrict the effective cooling of the superconductor because they cover the superconductor either in the tape form of wrapped on both side or impregnated. The implementation of rods or tubes will significantly enhance the cooling. Thus, effective heat transfer takes place from superconductor to coolant as they are directly in contact.
Thus, the superconducting tape in the entire winding pack remains in direct contact with the coolant except at the locations where there is a line contact between the superconductor tape and insulating rod. The area of this line contact can be

neglected compared to the total surface are of the tape which is in direct contact with the coolant.
In accordance with yet another embodiment of this invention, through slots (8) are provided on a first side plate (2). These slots (8) are radially dispersed about a central axis. These slots, typically, are relatively longer than the rods (5) placed adjacent each other.
Moreover, the slot provided for the insulating rods allows the rod to slide radially and hence reduces the strain during the coil contraction or expansion due to forces or temperature. This will help in recovery of superconductor tape during the event of quench. The gap between each turn is considered as per the standard insulation of air gap to ensure no voltage breakdown occurs between inter turns.
In accordance with still another embodiment of this invention, blind slotted grooves are provided on a second side plate (3) in order to arrest the movement of insulating rods in its longitudinal direction.
Reference numeral (6) refers to locking means such as screws. In accordance with an additional embodiment of this invention, peripheral holes are provided in the first side plate (2) as well as in the second side plate (3) in a matching manner such that the plates with the superconducting tapes may be stacked in a non-inductive fashion; i.e. spaced apart from adjacent such assemblies of plates and superconducting tapes. Reference numeral (9), (10), (11), and (12) (as illustrated in Figure 3 of the accompanying drawings) refer to coils assembled in non-inductive configurations for applications where inductance is not desired. In other applications, it can be assembled inductively.

Therefore, in the present design, the multi winding allows extended current density per turn of the winding; proper cooling as conductor is in direct contact with the coolant, sufficient gap between the turns by the insulating barrier rods. Moreover, during the cool down of the coil, contraction of the winding pack is also taken care by the movable barrier rods, thereby keeping the superconductor in un-stressed condition. In large winding packs, were coil inductance may hinder the smooth operation of the system, the inductance can be reduced by keeping two adjacent coils one over another such that the field direction in both the coils are opposite.
Hence, by the use of this invention, energy released during any off-normal scenarios leading to quenching of the system would be efficiently transferred to the coolant and the winding pack would be able to recover faster. Also, the thermal and electromagnetic hoop stresses are balanced by the movable rods in the winding pack.
Figure 4 illustrates a process of winding in a cryostat.
Reference numeral 17 refers to cryostat outer wall. Reference numeral 18 refers to cryostat inner wall. Reference numeral 19 refers to vacuum barrier of the cryostat. Reference numeral 13 refers to a liquid filling port. Reference numeral 14 refers to pressure relief valve. Reference numeral 15 refers to instrumentation feed through for voltage taps, temperature sensors, level sensors, hall probes, and the like. Reference numeral 16 refers to current leads connected to winding coil. Reference numeral 20 refers to wound coils in non-inductive / inductive manner, which wound coils are connected in series / parallel as per requirement. Reference numeral 15 refers to liquid coolant (generally liquid nitrogen or helium).

The advantages of the system and equipment of this invention lie in the following points:
1. The contact area between rod/tube with superconductor is minimum and hence, the cooling area for conductor is higher. Thus, this efficiently cools the winding during normal and quench cases;
2. Avoids the use of thermally poor insulations between turns and hence, increases the cooling power;
3. Provides flexibility to the winding during contraction and expansion due to temperature or electromagnetic forces;
4. Provides the required insulation strength between turns of the winding by introducing insulting rods of required diameters between the turns;
5. Makes the device compact with reduced number of turns for same rating with multiple superconductor tapes;
6. Increases the current density per turn by multiple windings of HTS tapes;
7. Reduces the number of parallel windings required in certain applications such as in fault current limiters;
8. Reduces the number of turns by an order of 'n' in certain applications such as in superconducting magnets;
9. Certain applications where inductance of the coil is an issue (fault current limiters), two coils can be kept one over another in opposite current flow direction to cancel the mutual flux;
10. Saves the cost of the insulation material;
11. The cooling is more efficient in the current invention because the coolant directly comes in contact with the superconductor tape almost everywhere in the winding. In applications like Fault Current Limiters, where large energy is released during fault operation, the absence of insulation layer

enables efficient extraction of the energy by the coolant during fault operations;
12. The rod type of arrangement provides flexibility, insulation strength, and reduces stress accumulation due to cool down;
13. In many applications, number of parallel disc winding which is required to achieve the current level, would be reduce by a factor of V. This would make the system compact and reduce cryogenic cost, cryostat size, etc;
14. For certain applications where coil inductance is not desired, two coils can be kept one over another with current flow in opposite direction such that their mutual effect is cancelled out; and
15. Current per unit turn can be increased to desired level by multi-paralleling of tape.
The technical advance of the current invention lies in the following points:
1. Efficient cooling of the conductor during operation using tubes or rods between inter turns as the maximum area of tape in the winding is directly in contact with the coolant;
2. Guiding slots to the inter-turn tube or rods in the flanges of bobbin gives flexibility during contraction and expansion or any electromechanical forces. This allows the thermal contraction of the winding pack without any strain accumulation. Hence, the critical current does not decrease due to the thermal strain;
3. Equi-spaced tubes or rod leads to higher cooling efficiency due to convective heat transfer;
4. Multiple winding for increased current density per turn, thereby reducing the total number of turns or total number of parallel coils depending on the application;

5. Increased current density per turn; and
6. The parallel arrangement of HTS tapes can be done in arrangement for anti-parallel flow of current, to effectively cancel the flux and the inductive effect.
According to an exemplary embodiment of a superconducting magnet, using the current invention, number of turn would reduce by an order of 2 or more and hence the magnet would be compact.
While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim,
1. Winding assembly with cooled superconductor tapes having localised inter-
turn insulation, said winding,assembly comprising:
a. one or two or more superconductor tapes being wound together over a
bobbin in order to enhance the current carrying capacity per turn, said
tapes being helical coils;
b. plurality of sets of rods, each set being formed by rods located adjacent
each other, longitudinally, number of adjacent rods corresponding to gaps
provisioned by turns of said tapes, said plurality of sets of rods being
radially dispersed about the wound superconducting tape(s);
c. first side plate and a second side plate adapted to cover said bobbin
wound superconducting tapes from an operative distal direction and an
operative proximal direction, correspondingly; and
d. slots being provided on said first side plates in a corresponding said
radially dispersed manner about a central axis, each of said slots being
relatively longer than the set of rods.
2. The assembly as claimed in claim 1, wherein said rods are insulating rods.
3. The assembly as claimed in claim 1, wherein said second side plate comprising blind slotted grooves in order to arrest the movement of said rods in their longitudinal direction.
4. The assembly as claimed in claim 1, wherein said bobbin is co-axial with said side-plates which form the upper and lower cover of said bobbin wound superconducting tapes.
5. The assembly as claimed in claim 1, wherein said rods are made from a

material selected from a group of materials consisting of Nylon, FRP, Teflon, or Mica tube.
6. The assembly as claimed in claim 1, wherein said gap between each turn is a pre-defined gap adapted to be considered as per standard insulation of air gap to ensure that no voltage breakdown occurs between inter turns.
7. The assembly as claimed in claim 1, wherein said assembly comprising peripheral holes in said first side plate as well as in said second side plate in a matching manner such that said plates with superconducting tapes may be stacked in a non-inductive fashion; i.e. spaced apart from adjacent such assemblies of plates and superconducting tapes.
8. The assembly as claimed in claim 1, wherein said one or more superconducting tapes are superconducting tapes which are wound together, in a parallel fashion, over a bobbin.
9. The assembly as claimed in claim 1, wherein said one or more superconducting tapes are superconducting tapes which are wound together, in an anti-parallel fashion, over a bobbin.
10. The assembly as claimed in claim 1, wherein said one or more superconducting tapes are superconducting tapes such that field direction of adjacent tapes are opposite.
11. The assembly as claimed in claim 1, wherein said rods are equi-spaced rods with a gap required as per the standard voltage clearance.