FIELD OF INVENTION
The present invention relates to a device for holding and insertably
assembling HTSC coils around the limb of High Temperature
Superconducting transformers. The invention further relates to a
method of assembling HSTC coils in high temperature
superconducting transformers.
BACKGROUND OF INVENTION
Coils manufactured with current carrying conductors for example,
copper adapted in conventional power transformers are sufficiently
thick and have mechanical strength of their own. These coils are
inserted around the limb of core of the transformer and are held in
position during operation of the transformer to enable withstanding
of electromagnetic forces.
High Temperature Superconductors (HTSC) presently available in the
art for example, BSCC02223 are delicate in nature as it has a very
thin layer of superconducting material at the center held in between
two thin stainless steel/copper/brass sheaths. In general HTSC
conductor is rectangular in shape and having a size of 4.0 mm width,
0.3 mm thick.
Coil turns are supported on a hollow cylinder called spool having
grooves on the outer surface to support the winding. These spools
are made of insulated material like Glass fiber Reinforced Plastic
(GFRP) which is compatible at 77K. Number of coils or spools are
decided according to the rating of the transformer, and are
connected in series/parallel. Each phase has sets of spools for HV
and LV winding.
In conventional transformers, copper coils are inserted around three
limbs of the transformer core. In HTSC transformer firstly the GFRP
containers are placed around each limb of the transformer. HV/LV
coils along with the holding structure can be inserted from the top.
These coils once put inside the container does not have accessibility
from outside for final manufacturing activities or inspection.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a device for
holding and assembling HSTC coils for inserting around the limbs of
high temperature superconducting transformers.
Another object of the invention is to propose a method for
assembling HSTC coils for inserting around the limb of high
temperature superconducting transformers.
SUMMARY OF THE INVENTION
According to the present invention, HV and LV coils made from
superconducting tape are assembled including all connections and
required insulation outside the container. These coils are secured in
place by at least one each top and bottom circular plate.
The top and bottom circular plates are connected by non-magnetic
insulating material for example, Bakelite rods having threads at both
ends. HV/LV coils are tightened with Bakelite nuts on both ends.
These Bakelite rods are extending outside from the top plate. With
this structure, the coils assembled outside the container, can be lifted
with the help of said top extended Bakelite rods. With the help of a
crane these assembled coils which now become a single unit are
inserted inside the GFRP container freely from the top of the
container. Three such assemblies are manufactured for a three-phase
transformer.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1A - Shows a device for holding the HV and LV spools in place1
according to the invention.
Figure 1B - Shows a plurality of grooves in the top and bottom plate
of the device of Figure 1A.
DETAILED DESCRIPTION OF THE INVENTION
HTSC tape is wound over a plurality of hollow GFRP spools having
continuous grooves along the surface of the spools. Number of such
spools depends upon the configuration and capacity of the
transformer and are connected together to make winding.
As shown in Figure 1 the LV winding (1) has a number of spools (la),
which are smaller in diameter than the HV winding (2) which again
has a number of spools (2a). A gap (G) between the HV and LV
winding (1,2) is maintained.
The device comprises :
A bottom plate (4) of substantially circular in shape, and annular type
which has a hole (9) in the center. One surface of this plate (4) has a
number of circular grooves (8) over the surface. Diameter and
number of grooves (8) match with the spool diameter of LV and HV
windings (1,2);
A top plate (3) is held on the top of spools (la,2a). These two plates
(3,4) are held together by tightening a plurality of adjustable
insulated Bakelite rods (5) for example at least six in numbers at
equal pitch;
An identical number of bakelite rods (6) are connected to the top
plate (3) and are used for lifting the HV and LV winding (1,2) along
with the device. The coil assembly can be lifted with these lifting rods
(6) and inserted into a double wall vacuum insulated torroidal type
GFRP container which surrounds the transformer.
The spools (la, 2a) along with the device are inserted inside the
container filled with liquid nitrogen.
All the constituent components of the device are made of insulated
material like Bakelite or glass fiber.
METHOD OF ASSEMBLY
The bottom plate (4) is connected with the at least six rods (5) and
Bakelite nuts (7) at bottom. The HV winding (2) spools (2a) are
placed in the grooves (8) on the top surface of the plate (3) and the
connected windings connected. Similarly the LV winding (1) spools
(1a) are placed. The top plate (3) is put over the spools (la) having
grooves (8) at the bottom surface and the winding connections are
done. The spools (la, 2a) are held in place by tightening the top and
bottom plate (3,4) with the help of the tightening/adjustment
Bakelite nuts (7) as shown in Figure 1B.
Another six number of Bakelite rods (6) are connected to the top
plate (3) with equal pitch and are used for lifting the windings (1,2)
along with device for inserting inside the container.

Three such structures are used for three phases of a HTSC
transformer.
According to the invention, the device enables an easy assembly of
the coils. Coils are assembled first with a circular plate (6) at the
bottom, placing the would spools (la, 2a) axially one inside the
other, placing top plate over the spools, tightening top and bottom
plate with Bakelite rods (5) and nuts (7). Connecting the lifting rods
(6) to the top plate (3). This assembly is done outside a GFRP
container or limb of the transformer core.
Six number of rod(s) are used to tighten the top and bottom plate
(3,4). It protects the HTSC windings from any mechanical damage to
the winding (1,2) while inserting inside the GFRP container.
With the help of the extended bars (6) at the top, another lifting
plate is connected for ease in lifting and inserting as it becomes a
single piece.
With this device it is possible to make correction for alignment and
inspection of the winding before inserting inside the container.
WE CLAIM
1. A device for holding and insertably assembling high
temperature superconducting (HSTC) coils around the limb of
HSTC transformers, comprising:
- a substantially circular shaped bottom plate (4) having a central
hole (9), a first surface of the bottom plate (4) provided with a
plurality of grooves (8) corresponding to the diameter of
grooves configured on HV and LV spools (la, 2a);
- a top plate (3) releasably connected to the bottom plate (4)
through a first plurality of bakelite rods (5), the HV and LV
spools (la, 2a) forming respectively the HV-winding (2) and LV-
winding (1) which being disposed inside the device by
maintaining a gap (G); and
- a second plurality of bakelite rods (6) connected to said first
plurality of rods (5) over the top plate (3) by means of bakelite
nuts (7), the second plurality of rods (6) being adaptable to lift
the device with the windings (1,2) by a crane and insert the
assembly into a vacuum insulated container which surrounds
the transformer.
2. A method for assembling HSTC coils for Inserting around the
limb of high temperature superconducting transformers,
comprising the steps of:
- placing the HV and LV spools (la, 2a) in the grooves (8) of the
bottom plate (4) and connecting the windings of each spool to
that of the adjacent spool;
- placing the top plate (3) over the spools (la, 2a) having
grooves;
- assembling the top plate (3) and the bottom plate (4) including
the spools (la, 2a) by placing a first plurality of bakeiite rods
(5) and tightening the assembly by adjusting nuts (7); and
- connecting a second plurality of bakeiite rods (6) over the top
plate (3) with adjusting nuts (7) for lifting the assembly and
insertion into a vacuum insulated container surrounding the
transformer.
3. A device for holding and insertably assembling high
temperature superconducting (HSTC) coils around the limb of
HSTC transformers as substantially described and illustrated
herein with reference to the accompanying drawings.

The invention relates to a device for holding and insertably
assembling high temperature superconducting (HSTC) coils around
the limb of HSTC transformers, comprising a substantially circular
shaped bottom plate (4) having a central hole (9), a first surface of
the bottom plate (4) provided with a plurality of grooves (8)
corresponding to the diameter of grooves configured on HV and LV
spools (1a, 2a);a top plate (3) releasably connected to the bottom
plate (4) through a first plurality of bakelite rods (5), the HV and LV
spools (la, 2a) forming respectively the HV-winding (2) and LV-
winding (1) which being disposed inside the device by maintaining a
gap (G); and a second plurality of bakelite rods (6) connected to said
first plurality of rods (5) over the top plate (3) by means of bakelite
nuts (7), the second plurality of rods (6) being adaptable to lift the
device with the windings (1,2) by a crane and insert the assembly
into a vacuum insulated container which surrounds the transformer.