Title of Invention	A METHOD OF PRODUCING FOR TURBO-GENERATOR STATOR WINDING WITH DOUBLE ROEBEL BAR DESIGN FOR OPTIMISATION OF SIZE AND IMPROVEMENT OF EFFICIENCY OF MACHINE
Abstract	This invention relates to a method of producing turbo generator stator with winding composed of end connection in Double Roebel bars and TG stator produced thereof comprising of making split between two turns of each top and bottom bar each turn having several insulated copper strips being Roebel transposed for 360 degrees; maintaining the split turns circumferentially and axially displaced from each other on connection side to facilitate gaps between two eye connections; constructing eye joints with strips to strip resistance brazing to minimize the eye joint copper losses during machine operation; constructing eye joints on the non-connection side in two tier by maintaining outer turn of an eye joint above the inner ore; providing eye joints on the connection side of the stator twice the number of those of the slots, but making the total extent of eye brazing same as number of slots, to form a double Roebel bar wound stator with optimized machine size with higher terminal voltage and lesser magnetic loading due to optimal size of the core and higher P/W (power/weight) ratio of the machine.

Title of Invention

A METHOD OF PRODUCING FOR TURBO-GENERATOR STATOR WINDING WITH DOUBLE ROEBEL BAR DESIGN FOR OPTIMISATION OF SIZE AND IMPROVEMENT OF EFFICIENCY OF MACHINE

Abstract

This invention relates to a method of producing turbo generator stator with winding composed of end connection in Double Roebel bars and TG stator produced thereof comprising of making split between two turns of each top and bottom bar each turn having several insulated copper strips being Roebel transposed for 360 degrees; maintaining the split turns circumferentially and axially displaced from each other on connection side to facilitate gaps between two eye connections; constructing eye joints with strips to strip resistance brazing to minimize the eye joint copper losses during machine operation; constructing eye joints on the non-connection side in two tier by maintaining outer turn of an eye joint above the inner ore; providing eye joints on the connection side of the stator twice the number of those of the slots, but making the total extent of eye brazing same as number of slots, to form a double Roebel bar wound stator with optimized machine size with higher terminal voltage and lesser magnetic loading due to optimal size of the core and higher P/W (power/weight) ratio of the machine.

Full Text	FIELD OF THE INVENTION The present invention relates to a method of TG stator with winding composed of end connection in Double Roebel bars made by split turns phase connection eye joints to achieve optimal size of the machine and higher functional efficiency. The proposed end winding of TG stator is applicable to 18-25 MV machines. BACKGROUND OF THE INVENTION Medium and large capacity generators stator coils are manufactured as an universal practice in half coil/bar form by all manufactures throughout the world. This is normally done keeping the size and weight of the bars in view as well as the ease of insertion of the coils/bars in the stator slots. During the process of winding assembly, the coils are placed/lowered in to the stator slots as per the winding scheme. Subsequently, the bars are electrically connected by soldering/brazing process to form phase groups. The individual end winding connections for a regular large capacity synchronous turbo generator stator is made either with strip to strip brazing or bunch brazing with or without a copper lug. Some manufacturers also practise soldering with a lug. All these practices depend upon the decision of techno-economics of end winding loss and cost involved in end winding connections. In the existing system of eye joint brazing in Turbo generators stator winding follow either strip to strip resistance brazing where the number of eye joints are same as those of number of slots on each side of the machine / winding. The major constrain in the existing sandwich winding practice is in end winding connection and the sizes of the machines are big with difficulties of transportation, high material cost and non-optimized magnetic loss. The proposed invention is aimed to solve the above difficulties of the prior state of art to develop a compact machine with optimized copper losses by employment of splitting the eye connection in connection side and making double tier connection of the turns in non-connection size. No prior art reference has been formed in the proposed field of development. DESCRIPTION OF THE INVENTION One of the objective of the invention is to provide a split between two turns of each top and bottom bar while effecting end winding connection between the two bars of the stator. Another objective of the invention is to maintain split turns circumferentially and axially displaced from each other in connection side to facilitate gaps between the two eye connections and thus to enable brazing of end winding connection. A still another objective of the invention is to construct the eye joints with strip to strip brazing to minimize the eye joint copper losses during machine operation ensuring minimum heat generation during brazing process and thus minimizing adverse effect on insulation of the bars. A further objective of the invention is to construct eye joints on the non- connection side in two tier i.e. outer turn of the eye joint above the inner one. A still further objective of the invention is to construct a double Roebel bar for the stator winding to optimize machine size with higher terminal voltage with lesser magnetic loading due to optimal size of the core, the machine length being reduced by 20% and end winding losses by 10% from the existing double Roebel bar generator stator. A yet another objective of the invention is to provide eye joints on the connection side of the machine twice the number of those of the slots, but making the total extent of eye brazing work same. The proposed invention is aimed with the above mentioned objectives of the invention to develop an improved compact machine with a double Roebel bar design of stator, by removing the major constraint in the sandwich design in end winding connection. In the present method, a double Roebel bar was designed for the stator winding to optimize the machine size. The individual turn has several insulated copper strips which are Roebel transposed for 360 degrees. The twin turns require a split in the eye join zone to make the connection between truns from one slot to another. However, as the size of the individual turn being very large, the end connection is not possible with the number of eyes same as those of the number of slots. Hence, a new end connection detail was designed to meet the requirement, by splitting the eye connection in connection side and making double tier connection of the turns in non-connection side. According to the present invention there is provided a method of producing turbo generator stator with winding composed of end connection in Double Roebel bars comprising of making split between two turns of each top and bottom bar, each turn having several insulated copper strips being Roebel transposed for 360 degrees; maintaining the split turns circumferentially and axially displaced from each other on connection side to facilitate gaps between two eye connections; constructing eye joints with strips to strip resistance brazing to minimize the eye joint copper losses during machine operation; constructing eye joints on the non- connection side in two tier by maintaining outer turn of an eye joint above the inner one; providing eye joints on the connection side of the stator twice the number of those of the slots, but making the total extent of eye brazing same as number of slots, to form a double Roebel bar wound stator with optimized machine size with higher terminal voltage and lesser magnetic loading due to optimal size of the core and higher P/W (power / weight) ratio of the machine. The proposed invention will be better understood by the following description with reference to the accompanying drawings in which Figure 1 shows schematically stator bar construction details showing split turn on exciter/connection side and top turn and bottom turn of copper strips of the bars. Figure 2 shows schematically details of stator winding end connection with overhang details on exciter side and on Transposition side with slot cross section and showing inner and outer phase connector and strip brazing with outer and inner eye joint on the end winding side and inner and outer joint on transposition side according to the invention. Figure 3 shows details of stator winding end connection showing the composition of connection on ES and TS side according to the invention. Figure 4 represents a schematic diagram showing the details of Y connected, turbo generator stator winding for end connections with double Roebel bars according to the present invention, on Transposition and Exciter side. Figure 5 shows overhang details on End slot for single Roebel Bar with phase connection detail. Figure 6 shows in details overhang details on E.S side for double Roebel bar with inner eye and outer eye details according to the invention. Figure 7 shows a photographic view of construction of Roebel bars according to the invention. Figure 8 shows a photographic view of a TG stator winding of overhang showing the manner of inner and outer eye joint prepared according to the invention. Figure 9 shows a photographic view of a TG stator winding of overhang portion, showing the manner of outer eye joint and inner eye joint prepared according to the invention. Figure 10 shows a photographic view of a TG stator winding of overhang showing locations of phase connector provided according to the invention. Figure 4 shows the scheme of stator winding with the following technical data The stator winding scheme has been designed with 2 pole, 3000 rpm, star connected, 3 phase double layer lap mode with the following technical specification: No. of slots : 42 No. of poles : 2 No. of phases : 3 No of slots/poles/phase : 7 Pitch : 17/21 No. of parallel paths : 2 Connection : Y The double bars details shown in Figure 1 are as follows No. of strips : 2x 18 all insulated 2.15 x 9.75, pitch : 17/21, Involute: 13/20 Degrees, No. of turns/bar: 2 Roebel Transposition : 360 degrees. The stator bars are with two turns, individual turns are with insulated strips, which are transposed for 360 degrees. Turns are individually insulated before being stacked one above other and the turns are with inner potential grading. Overall insulation is provided for ground wall of the bars for the rated voltage of the machine. Main Components of a Bar: Bars are components of generator stator windings, also called conductors to carry current to be delivered to the output leads and subsequently to the transmission lines through transformer. The bars of large machines are made of several insulated copper conductors electrically isolated from each other by suitable materials before application of high voltage insulation. The insulation of the strips are normally glass based and the high voltage insulation is usually mica glass epoxy based to meet the voltage stress requirement. Roebel Bars as conductors are illustrated in Figure 7. The name Roebel is derived from the inventor Mr. Robert Roebel, the British Scientist and Engineer, who invented the concept of transposition of strips in a plaited way to equalize the flux linkage among all the strips irrespective of their differential radial distance from the flux generating plane. This results in equal induced voltage generation among all the strips of the bar and avoid inter strip circulating short circuiting current. In a Roebel bar, all the strips travel from top to bottom and then up to the original top level (As done in plaiting of the hair strands of women). This is called 360 degrees transposition. Depending upon the requirement, the transposition may be repeated or may be continuous in the active length of the machine. Normally the Roebel Bar design of the stator are used for medium sized high voltage generator stator winding. In such case, either single or double layer star connected lap winding design is adopted. In case of the Roebel bars, several insulated copper strips aretransposed in single/two planes to minimize the copper losses due to any possible difference in the induced electro motive force (EMF) among the copper strips. In smaller machines with limitation of magnetic loading with higher terminal voltage requirement, the winding is designed with multi turn bars. In the present design of the machine, both the design concepts of Roebel transposition and multiturn winding features are integrated to achieve optimal size of the machine. A novel attempt has been made to make the end connection of the double turn Roebel bar with optimal use of copper and minimal eye connection losses, which has been illustrated in Figure 1. Details of the End winding Connection 1. The function of end connection of the winding is to complete the winding scheme as per the design requirement with minimum copper and maximum rigidity. 2. The end connections of (i) Regular mid phase eye joints and (ii) Phase connection eye joint have been specially constructed with split turns to make the double Roebel bars connected as per the winding scheme, which have been illustrated in Figures 2 and 3 and Figures 7 to 10. 3. The number of eye joints are made twice the number of those of slots to make the scheme possible. 4. Necessary axial gap between phase connectors is provided to withstand the voltage stress. Overhang eye connection details for single roebel. bars and details of overhang for Double roebel bars, both with strip to strip brazing/lug brazing have been illustrated in Figures 5 and 6 respectively. Keeping the basic objective of optimization of the machine size, the double Roebel bars were constructed for the winding of the turbo generator stator. The stator bars individual turns were constructed with Roebel transposition of insulated coppers strips. Necessary inner potential grading system in the main insulation was provided to keep the voltage stress in the bars minimum. The unique design of double Roebel bars end connection with twice the number of eye joints was adopted to optimize the machine size. The split turn in the eye joint of the bars in connection side makes the phase group formation possible with optimal size of the winding overhang and all the eye joints are accommodated within the circumference of the winding. - The basic principal of end connection of the overhang winding is based on twin objective of (i) optimal and rigid overhang length and (ii) optimal end winding losses. This resulted in optimization of size of the generator and higher efficiency. - The number of eye joints made were twice as those of the slots. A split was envisaged at end connections to ensure separate eye joints. The eye joints were displaced circumferentially and axially into inner eye joints and outer eye joints to make the adequate gaps for the work men to make jointing / brazing work. - The eye joint was designed with strip to strip resistance brazing to minimize the joint copper loss and heat generated during the brazing work. - The phase connections were adopted with axial shift at the same circumferential location with necessary gap between joints to withstand the voltage stress. The Double Roebel Bar design of Stator Winding fulfills the following: - Generation of higher voltage in lesser active length of the machine. - Lesser magnetic losses due to optimal size of the core thus higher machine efficiency. - Higher P/W (Power/Weight) ratio of the machine The proposed method of end winding connection ensured the possibility of making winding scheme with twin/double Roebel bars and minimized the end winding losses. This type of end winding connection is suitable for the range of machines from 18-25 MW, where the machine length is optimized with adaptation of twin Roebel bars. The invention as herein narrated with an exemplary embodiment should not be read and construed in a restrictive manner, as various modifications, alterations and adaptations are possible with in the scope and ambit of the invention as defined in the encompassed appended claims. WE CLAIM 1. A method of producing Turbo generator stator winding with double Roebel bars having eye connection with split eye joints, the said method comprising; providing eye joints in the double Roebel bars in the connection side of the machine twice the number of the number of slots; constructing the eye joint with split turns to make the double roebel bars connected as per the winding scheme; displacing the eye joints circumferentially and axially into inner eye joints and outer eye joints to make the adequate gaps for brazing work; allowing axial gap between phase connectors to withstand the voltage stress; arranging the eye joints in two tier in non connection side making outer turn of eye joint one above the other; wherein the eye joints are constructed with strip brazing to minimize the eye joint copper losses during machine operation ensuring optimal and rigid overhang length and optimal winding losses resulting optimization and higher efficiency of the generator. 2. The method of producing turbo generator stator as claimed in claim 1 wherein strip to strip resistance brazing reduce eye connection copper losses upto 10 percent due to reduced size of the machine in length by 20 percent. 3. The method of producing turbo generator stator as claimed in claim 1 wherein the stator winding has been constructed with 2 pole, 300 rpm, star connected, 3 phase as 7, pitch 17/21, number of parallel paths as 2 and with Y connection according to the stator winding scheme as shown in Figure 4. 4. The method of producing turbo generator stator as claimed in the preceding claims wherein the double bar details are provided as number strips - 2 x 18 all insulated 2.15 x 9.75, pitch 17/21, involute-13/20 degrees, number of turns / bar - 2, Roebel Transposition - 360 degrees, as represented in Figure 1. 5. The method of producing turbo generator stator as claimed in claim 4 wherein the stator bars are provided with two turns, individual turns being provided with insulated strips transposed for 360 degrees, the turns being individually insulated before stacking one above the other, the turns being with inner potential grading and overall insulation being provided for ground wall of the bars for the rated voltage of the machine. 6. A method of producing turbo generator stator as claimed in the preceding claims wherein 360 degrees transposition Roebel bars as conductors is composed by adapting all the strips traveling from top to bottom and then upto the original top level as like in plaiting of the hair strands of women, the said transposition being repeated or maintained continuous in the active length of the machine as shown in Figure 7. 7. A method of producing turbo generator stator as claimed in the preceding claims wherein the end connections of regular mid phase eye joints and phase connection eye joint are constructed with split turns to make the double bars connected as per the winding scheme. 8. The method of producing turbo generator stator as claimed in the preceding claims wherein the end connections in double Roebel bars with split turns in the eye joints of the bars in connection side enable to make the phase group formation possible with optimal size of the winding overhang and accommodating all the eye joints within the circumference of the winding on integrating the features Roebel transposition and multi turn winding features to achieve optimal size of the machine. 9. A method of producing turbo generator stator with winding composed of end connections in double Roebel bars as herein described and illustrated in the accompanying drawings. ABSTRACT A METHOD OF PRODUCING FOR TURBO-GENERATOR STATOR WINDING WITH DOUBLE ROEBEL BAR DESIGN FOR OPTIMISATION OF SIZE AND IMPROVEMENT OF EFFICIENCY OF MACHINE This invention relates to a method of producing turbo generator stator with winding composed of end connection in Double Roebel bars and TG stator produced thereof comprising of making split between two turns of each top and bottom bar each turn having several insulated copper strips being Roebel transposed for 360 degrees; maintaining the split turns circumferentially and axially displaced from each other on connection side to facilitate gaps between two eye connections; constructing eye joints with strips to strip resistance brazing to minimize the eye joint copper losses during machine operation; constructing eye joints on the non-connection side in two tier by maintaining outer turn of an eye joint above the inner ore; providing eye joints on the connection side of the stator twice the number of those of the slots, but making the total extent of eye brazing same as number of slots, to form a double Roebel bar wound stator with optimized machine size with higher terminal voltage and lesser magnetic loading due to optimal size of the core and higher P/W (power/weight) ratio of the machine.

Full Text

FIELD OF THE INVENTION
The present invention relates to a method of TG stator with winding composed
of end connection in Double Roebel bars made by split turns phase connection
eye joints to achieve optimal size of the machine and higher functional efficiency.
The proposed end winding of TG stator is applicable to 18-25 MV machines.
BACKGROUND OF THE INVENTION
Medium and large capacity generators stator coils are manufactured as an
universal practice in half coil/bar form by all manufactures throughout the world.
This is normally done keeping the size and weight of the bars in view as well as
the ease of insertion of the coils/bars in the stator slots. During the process of
winding assembly, the coils are placed/lowered in to the stator slots as per the
winding scheme. Subsequently, the bars are electrically connected by
soldering/brazing process to form phase groups.

The individual end winding connections for a regular large capacity synchronous
turbo generator stator is made either with strip to strip brazing or bunch brazing
with or without a copper lug. Some manufacturers also practise soldering with a
lug. All these practices depend upon the decision of techno-economics of end
winding loss and cost involved in end winding connections.
In the existing system of eye joint brazing in Turbo generators stator winding
follow either strip to strip resistance brazing where the number of eye joints are
same as those of number of slots on each side of the machine / winding.
The major constrain in the existing sandwich winding practice is in end winding
connection and the sizes of the machines are big with difficulties of
transportation, high material cost and non-optimized magnetic loss.
The proposed invention is aimed to solve the above difficulties of the prior state
of art to develop a compact machine with optimized copper losses by
employment of splitting the eye connection in connection side and making
double tier connection of the turns in non-connection size.
No prior art reference has been formed in the proposed field of development.

DESCRIPTION OF THE INVENTION
One of the objective of the invention is to provide a split between two turns of
each top and bottom bar while effecting end winding connection between the
two bars of the stator.
Another objective of the invention is to maintain split turns circumferentially and
axially displaced from each other in connection side to facilitate gaps between
the two eye connections and thus to enable brazing of end winding connection.
A still another objective of the invention is to construct the eye joints with strip
to strip brazing to minimize the eye joint copper losses during machine operation
ensuring minimum heat generation during brazing process and thus minimizing
adverse effect on insulation of the bars.
A further objective of the invention is to construct eye joints on the non-
connection side in two tier i.e. outer turn of the eye joint above the inner one.

A still further objective of the invention is to construct a double Roebel bar for
the stator winding to optimize machine size with higher terminal voltage with
lesser magnetic loading due to optimal size of the core, the machine length being
reduced by 20% and end winding losses by 10% from the existing double Roebel
bar generator stator.
A yet another objective of the invention is to provide eye joints on the
connection side of the machine twice the number of those of the slots, but
making the total extent of eye brazing work same.
The proposed invention is aimed with the above mentioned objectives of the
invention to develop an improved compact machine with a double Roebel bar
design of stator, by removing the major constraint in the sandwich design in end
winding connection.
In the present method, a double Roebel bar was designed for the stator winding
to optimize the machine size. The individual turn has several insulated copper
strips which are Roebel transposed for 360 degrees. The twin turns require a
split in the eye join zone to make the connection between truns from one slot to
another. However, as the size of the individual turn being very large, the end

connection is not possible with the number of eyes same as those of the number
of slots. Hence, a new end connection detail was designed to meet the
requirement, by splitting the eye connection in connection side and making
double tier connection of the turns in non-connection side.
According to the present invention there is provided a method of producing turbo
generator stator with winding composed of end connection in Double Roebel
bars comprising of making split between two turns of each top and bottom bar,
each turn having several insulated copper strips being Roebel transposed for 360
degrees; maintaining the split turns circumferentially and axially displaced from
each other on connection side to facilitate gaps between two eye connections;
constructing eye joints with strips to strip resistance brazing to minimize the eye
joint copper losses during machine operation; constructing eye joints on the non-
connection side in two tier by maintaining outer turn of an eye joint above the
inner one; providing eye joints on the connection side of the stator twice the
number of those of the slots, but making the total extent of eye brazing same as
number of slots, to form a double Roebel bar wound stator with optimized
machine size with higher terminal voltage and lesser magnetic loading due to
optimal size of the core and higher P/W (power / weight) ratio of the machine.

The proposed invention will be better understood by the following description
with reference to the accompanying drawings in which
Figure 1 shows schematically stator bar construction details
showing split turn on exciter/connection side and top
turn and bottom turn of copper strips of the bars.
Figure 2 shows schematically details of stator winding end
connection with overhang details on exciter side
and on Transposition side with slot cross section
and showing inner and outer phase connector and
strip brazing with outer and inner eye joint on the end
winding side and inner and outer joint on transposition
side according to the invention.
Figure 3 shows details of stator winding end connection
showing the composition of connection on ES
and TS side according to the invention.

Figure 4 represents a schematic diagram showing the details of
Y connected, turbo generator stator winding for end
connections with double Roebel bars according to
the present invention, on Transposition and Exciter side.
Figure 5 shows overhang details on End slot for single
Roebel Bar with phase connection detail.
Figure 6 shows in details overhang details on E.S side for double Roebel bar
with inner eye and outer eye details according to the invention.
Figure 7 shows a photographic view of construction of
Roebel bars according to the invention.
Figure 8 shows a photographic view of a TG stator winding of
overhang showing the manner of inner and outer eye
joint prepared according to the invention.

Figure 9 shows a photographic view of a TG stator winding of
overhang portion, showing the manner of outer eye joint
and inner eye joint prepared according to the invention.
Figure 10 shows a photographic view of a TG stator winding
of overhang showing locations of phase connector
provided according to the invention.
Figure 4 shows the scheme of stator winding
with the following technical data
The stator winding scheme has been designed with 2 pole, 3000 rpm, star
connected, 3 phase double layer lap mode with the following technical
specification:
No. of slots : 42
No. of poles : 2
No. of phases : 3
No of slots/poles/phase : 7
Pitch : 17/21
No. of parallel paths : 2
Connection : Y

The double bars details shown in Figure 1 are as follows
No. of strips : 2x 18 all insulated 2.15 x 9.75, pitch : 17/21, Involute:
13/20 Degrees, No. of turns/bar: 2
Roebel Transposition : 360 degrees.
The stator bars are with two turns, individual turns are with insulated strips,
which are transposed for 360 degrees. Turns are individually insulated before
being stacked one above other and the turns are with inner potential grading.
Overall insulation is provided for ground wall of the bars for the rated voltage of
the machine.
Main Components of a Bar:
Bars are components of generator stator windings, also called conductors to
carry current to be delivered to the output leads and subsequently to the
transmission lines through transformer. The bars of large machines are made of
several insulated copper conductors electrically isolated from each other by
suitable materials before application of high voltage insulation. The insulation of
the strips are normally glass based and the high voltage insulation is usually mica
glass epoxy based to meet the voltage stress requirement.

Roebel Bars as conductors are illustrated in Figure 7.
The name Roebel is derived from the inventor Mr. Robert Roebel, the British
Scientist and Engineer, who invented the concept of transposition of strips in a
plaited way to equalize the flux linkage among all the strips irrespective of their
differential radial distance from the flux generating plane. This results in equal
induced voltage generation among all the strips of the bar and avoid inter strip
circulating short circuiting current. In a Roebel bar, all the strips travel from top
to bottom and then up to the original top level (As done in plaiting of the hair
strands of women). This is called 360 degrees transposition. Depending upon the
requirement, the transposition may be repeated or may be continuous in the
active length of the machine.
Normally the Roebel Bar design of the stator are used for medium sized high
voltage generator stator winding. In such case, either single or double layer star
connected lap winding design is adopted. In case of the Roebel bars, several
insulated copper strips aretransposed in single/two planes to minimize the

copper losses due to any possible difference in the induced electro motive force
(EMF) among the copper strips. In smaller machines with limitation of magnetic
loading with higher terminal voltage requirement, the winding is designed with
multi turn bars. In the present design of the machine, both the design concepts
of Roebel transposition and multiturn winding features are integrated to achieve
optimal size of the machine. A novel attempt has been made to make the end
connection of the double turn Roebel bar with optimal use of copper and minimal
eye connection losses, which has been illustrated in Figure 1.
Details of the End winding Connection
1. The function of end connection of the winding is to complete the winding
scheme as per the design requirement with minimum copper and
maximum rigidity.
2. The end connections of (i) Regular mid phase eye joints and (ii) Phase
connection eye joint have been specially constructed with split turns to
make the double Roebel bars connected as per the winding scheme,
which have been illustrated in Figures 2 and 3 and Figures 7 to 10.

3. The number of eye joints are made twice the number of those of slots to
make the scheme possible.
4. Necessary axial gap between phase connectors is provided to withstand
the voltage stress.
Overhang eye connection details for single roebel. bars and details of overhang
for Double roebel bars, both with strip to strip brazing/lug brazing have been
illustrated in Figures 5 and 6 respectively.
Keeping the basic objective of optimization of the machine size, the double
Roebel bars were constructed for the winding of the turbo generator stator.
The stator bars individual turns were constructed with Roebel transposition of
insulated coppers strips. Necessary inner potential grading system in the main
insulation was provided to keep the voltage stress in the bars minimum.

The unique design of double Roebel bars end connection with twice the number
of eye joints was adopted to optimize the machine size. The split turn in the eye
joint of the bars in connection side makes the phase group formation possible
with optimal size of the winding overhang and all the eye joints are
accommodated within the circumference of the winding.
- The basic principal of end connection of the overhang winding is based on twin
objective of (i) optimal and rigid overhang length and (ii) optimal end winding
losses. This resulted in optimization of size of the generator and higher
efficiency.
- The number of eye joints made were twice as those of the slots. A split was
envisaged at end connections to ensure separate eye joints. The eye joints were
displaced circumferentially and axially into inner eye joints and outer eye joints
to make the adequate gaps for the work men to make jointing / brazing work.
- The eye joint was designed with strip to strip resistance brazing to minimize the
joint copper loss and heat generated during the brazing work.

- The phase connections were adopted with axial shift at the same
circumferential location with necessary gap between joints to withstand the
voltage stress.
The Double Roebel Bar design of Stator Winding fulfills the following:
- Generation of higher voltage in lesser active length of the machine.
- Lesser magnetic losses due to optimal size of the core thus higher
machine efficiency.
- Higher P/W (Power/Weight) ratio of the machine
The proposed method of end winding connection ensured the possibility of
making winding scheme with twin/double Roebel bars and minimized the end
winding losses. This type of end winding connection is suitable for the range of
machines from 18-25 MW, where the machine length is optimized with
adaptation of twin Roebel bars.

The invention as herein narrated with an exemplary embodiment should not be
read and construed in a restrictive manner, as various modifications, alterations
and adaptations are possible with in the scope and ambit of the invention as
defined in the encompassed appended claims.

WE CLAIM
1. A method of producing Turbo generator stator winding with double Roebel bars
having eye connection with split eye joints, the said method comprising;
providing eye joints in the double Roebel bars in the connection side of the
machine twice the number of the number of slots;
constructing the eye joint with split turns to make the double roebel bars
connected as per the winding scheme;
displacing the eye joints circumferentially and axially into inner eye joints and
outer eye joints to make the adequate gaps for brazing work;
allowing axial gap between phase connectors to withstand the voltage stress;
arranging the eye joints in two tier in non connection side making outer turn of
eye joint one above the other;
wherein the eye joints are constructed with strip brazing to minimize the eye
joint copper losses during machine operation ensuring optimal and rigid
overhang length and optimal winding losses resulting optimization and higher
efficiency of the generator.

2. The method of producing turbo generator stator as claimed in claim 1 wherein
strip to strip resistance brazing reduce eye connection copper losses upto 10
percent due to reduced size of the machine in length by 20 percent.
3. The method of producing turbo generator stator as claimed in claim 1 wherein
the stator winding has been constructed with 2 pole, 300 rpm, star connected,
3 phase as 7, pitch 17/21, number of parallel paths as 2 and with Y connection
according to the stator winding scheme as shown in Figure 4.
4. The method of producing turbo generator stator as claimed in the preceding
claims wherein the double bar details are provided as number strips - 2 x 18 all
insulated 2.15 x 9.75, pitch 17/21, involute-13/20 degrees, number of turns /
bar - 2, Roebel Transposition - 360 degrees, as represented in Figure 1.

5. The method of producing turbo generator stator as claimed in claim 4 wherein
the stator bars are provided with two turns, individual turns being provided
with insulated strips transposed for 360 degrees, the turns being individually
insulated before stacking one above the other, the turns being with inner
potential grading and overall insulation being provided for ground wall of the
bars for the rated voltage of the machine.
6. A method of producing turbo generator stator as claimed in the preceding
claims wherein 360 degrees transposition Roebel bars as conductors is
composed by adapting all the strips traveling from top to bottom and then upto
the original top level as like in plaiting of the hair strands of women, the said
transposition being repeated or maintained continuous in the active length of
the machine as shown in Figure 7.
7. A method of producing turbo generator stator as claimed in the preceding
claims wherein the end connections of regular mid phase eye joints and phase
connection eye joint are constructed with split turns to make the double bars
connected as per the winding scheme.

8. The method of producing turbo generator stator as claimed in the preceding
claims wherein the end connections in double Roebel bars with split turns in
the eye joints of the bars in connection side enable to make the phase group
formation possible with optimal size of the winding overhang and
accommodating all the eye joints within the circumference of the winding on
integrating the features Roebel transposition and multi turn winding features to
achieve optimal size of the machine.
9. A method of producing turbo generator stator with winding composed of end
connections in double Roebel bars as herein described and illustrated in the
accompanying drawings.

ABSTRACT

A METHOD OF PRODUCING FOR TURBO-GENERATOR STATOR WINDING
WITH DOUBLE ROEBEL BAR DESIGN FOR OPTIMISATION OF SIZE AND
IMPROVEMENT OF EFFICIENCY OF MACHINE
This invention relates to a method of producing turbo generator stator with winding
composed of end connection in Double Roebel bars and TG stator produced thereof
comprising of making split between two turns of each top and bottom bar each turn
having several insulated copper strips being Roebel transposed for 360 degrees;
maintaining the split turns circumferentially and axially displaced from each other on
connection side to facilitate gaps between two eye connections; constructing eye
joints with strips to strip resistance brazing to minimize the eye joint copper losses
during machine operation; constructing eye joints on the non-connection side in two
tier by maintaining outer turn of an eye joint above the inner ore; providing eye joints
on the connection side of the stator twice the number of those of the slots, but
making the total extent of eye brazing same as number of slots, to form a double
Roebel bar wound stator with optimized machine size with higher terminal voltage and
lesser magnetic loading due to optimal size of the core and higher P/W
(power/weight) ratio of the machine.

Documents:

00470-kol-2007-abstract.pdf

00470-kol-2007-claims.pdf

00470-kol-2007-correspondence others 1.1.pdf

00470-kol-2007-correspondence others.pdf

00470-kol-2007-description complete.pdf

00470-kol-2007-drawings.pdf

00470-kol-2007-form 1.pdf

00470-kol-2007-form 18.pdf

00470-kol-2007-form 2.pdf

00470-kol-2007-form 3.pdf

00470-kol-2007-gpa.pdf

470-KOL-2007-(01-10-2012)-ABSTRACT.pdf

470-KOL-2007-(01-10-2012)-CLAIMS.pdf

470-KOL-2007-(01-10-2012)-CORRESPONDENCE.pdf

470-KOL-2007-(01-10-2012)-DRAWINGS.pdf

470-KOL-2007-(01-10-2012)-FORM-1.pdf

470-KOL-2007-(01-10-2012)-FORM-13.pdf

470-KOL-2007-(01-10-2012)-FORM-2.pdf

470-KOL-2007-(01-10-2012)-PA.pdf

470-KOL-2007-(06-07-2012)-CORRESPONDENCE.pdf

470-KOL-2007-(22-12-2011)-ABSTRACT.pdf

470-KOL-2007-(22-12-2011)-AMANDED CLAIMS.pdf

470-KOL-2007-(22-12-2011)-DESCRIPTION (COMPLETE).pdf

470-KOL-2007-(22-12-2011)-DRAWINGS.pdf

470-KOL-2007-(22-12-2011)-EXAMINATION REPORT REPLY RECIEVED.PDF

470-KOL-2007-(22-12-2011)-FORM-1.pdf

470-KOL-2007-(22-12-2011)-FORM-2.pdf

470-KOL-2007-(22-12-2011)-OTHERS.pdf

470-kol-2007-CANCELLED PAGES.pdf

470-kol-2007-CORRESPONDENCE-1.1.pdf

470-KOL-2007-CORRESPONDENCE.pdf

470-kol-2007-EXAMINATION REPORT.pdf

470-kol-2007-FORM 13.pdf

470-kol-2007-FORM 18.pdf

470-kol-2007-GPA.pdf

470-kol-2007-GRANTED-ABSTRACT.pdf

470-kol-2007-GRANTED-CLAIMS.pdf

470-kol-2007-GRANTED-DESCRIPTION (COMPLETE).pdf

470-kol-2007-GRANTED-DRAWINGS.pdf

470-kol-2007-GRANTED-FORM 1.pdf

470-kol-2007-GRANTED-FORM 2.pdf

470-kol-2007-GRANTED-FORM 3.pdf

470-kol-2007-GRANTED-SPECIFICATION-COMPLETE.pdf

470-kol-2007-REPLY TO EXAMINATION REPORT.pdf

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Patent Number

262618

Indian Patent Application Number

470/KOL/2007

PG Journal Number

36/2014

Publication Date

05-Sep-2014

Grant Date

29-Aug-2014

Date of Filing

26-Mar-2007

Name of Patentee

BHARAT HEAVY ELECTRICALS LIMITED

Applicant Address

REGIONAL OPERATIONS DIVISION (ROD), PLOT NO : 9/1, DJBLOCK 3RD FLOOR, KARUNAMOYEE, SALT LAKE CITY, KOLKATA-700091, HAVING ITS REGISTERED OFFICE AT BHEL HOUSE, SIRI FORT, NEW DELHI- 110049

Inventors:

#	Inventor's Name	Inventor's Address
1	ACHARYA, RATNANAV	ELECTRICAL MACHINES ENGINEERING, BHARAT HEAVY ELECTRICALS LIMITED., RAMACHANDRAPURAM, HYDERABAD-502032

PCT International Classification Number

H02K3/28

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA