FIELD OF THE INVENTON
The present invention relates to a process for safe manufacturing of improved slot
wedges disposed in stators of large size Turbo-Generator.
BACKGROUND OF THE INVENTION
Slot wedges are used in stator of all ratings of large size Turbo-Generator, generally the
one used in thermal power plants. Stator consists of stator frame, stator core, stator
winding, spring and spring basket, magnetic shunt, press rings and end shield.
Stator frame: It is made up of structural steel. Stator core is situated in stator frame.
Stator core: It is made of silicon steel with high permeability and low hysteresis and
eddy current losses. The sheets are suspended in the stator frame from insulated guide
bars. Stator laminations are coated with synthetic varnish. In order to minimize eddy
current losses of rotating magnetic flux which interact with the core is built of thin
laminations. Each lamination layer is made of individual segments. Core is mainly used
for efficiently carrying electrical and mechanical flux. It is inserted vertically in frame.
Stator winding: When rotating magnetic flux is link with copper made windings then
emf induced in stator windings. The bar consists of solid and hollow stands distributed
over the entire bar cross-section so that good heat dissipation is insured at the bar ends
Spring and spring basket: The lower spring prevents a lateral deflection of the core.
The flats spring are resilient to the radial movement of the core suspension points and
will largely resist transmission of frequency of vibration to the frame.
Magnetic shunt: It is a type of rings which is used to confine he magnetic flux with the
stator, one ring is connected on turbine end and one ring is connected at exciter end.
These rings are made up of steel.

Press rings: The press rings is bolted to the end of core bars. Pressure of the press
ring is transmitted to stator core stampings through press fringes of non- magnetic steel
and duralumin placed adjacent to press ring.
End Shield: The end covers are made up of fabricated steel. They are employed with
guide vans on inner side for ensuring uniform distribution of air cool air flows from sides
and hot air flows in Centre. Rotor fan sucks the hot air which then passes through
compressor and gets cool and circulate to core. They are used to hold the bearings and
shaft seal assembly. It is mounted on both the ends of the stator.
Slot wedges are used in stator of turbo generator. Slot wedges are fitted after laying of
upper bars. Slot wedges are made of phenolic laminated cotton fabric sheet (Grade-f4)
for turbo-generator ratings such as 500MW, 600MW, 660MW, 700MW, 800MW and
epoxy laminated glass fabric base sheet (Glass textolite, G-2) for 250 MW turbo-
generator. Slot wedges are required in huge quantity i.e. around 1 thousand. There is
requirement of high accuracy in dimension of slot wedges during assembly in core slots.
In the existing practice there was no arrangement to hold slot wedge on bed of milling
machine. Therefore, manufacturing of the slot wedge was done by taking tolerance in
thickness and width of process, enormous problems were faced like additional man-
power was required to maintain dimensions of wedge. Quality of finished product was
affected because in absence of no proper arrangement to machining of slot wedge
which ultimately causing less productivity because of increase of cycle time of
manufacture and in case of failure during quality control check further increasing cycle
time, as well as increased material wastage because of high rejection rate.
OBJECTS OF THE INVENTION
It is therefore an object of the invention is to propose a process for safe manufacturing
of improved slot wedges disposed in stators of large size Turbo-Generator.
Another object of the invention is to a process for safe manufacturing of improved slot

wedges disposed in stators of large size Turbo-Generator which reduces the
manufacturing cycle time.
A further object of the invention is to propose a process for safe manufacturing of
improved slot wedges disposed in stators of large size Turbo-Generator which allows
manufacture slot wedges with less variation from standard dimensions.
Yet further object of the invention is to propose a process for safe manufacturing of
improved slot wedges disposed in stators of large size Turbo-Generator which produces
slot wedges which reduced cost of production by minimizing the waste in rework.
A still further object of the invention is to propose a process for safe manufacturing of
improved slot wedges disposed in stators of large size Turbo-Generator, which allows
manufacture of slot wedges at vertical milling machine
SUMMARY OF THE INVENTION
Accordingly there is provided, a process for safe manufacturing of improved slot
wedges disposed in stators of large size Turbo-Generator, comprising the steps of a
process for safe manufacturing of improved slot wedges disposed in the stators of large
size Turbo-Generator cutting a blank for making a fixture providing an insertion key
at the bottom of the blank for locking into T-slot of a milling machine’s bed; cutting a
step in the blank at both end of the fixture for holding the fixture by threaded means;
providing a plurality of threaded holes below said step for tightening of the fixture with
the help of the threaded means at milling machine’s bed cutting a rectangular slot for
putting a slot wedge into the fixture; plurality of threaded hole with threads of
corresponding size for tightening the slot wedge by tightening bolt of respective size
and to minimize vibration of the slot wedge during machining of the slot wedge (job)
profile (30 degree angle) on the milling machine; and inserting specific size of packing
to maintain the gap between the slot wedge the and fixture for different ratings of
Turbo-Generator.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The foregoing and other features of the invention will be apparent from the following
more particular description of the invention, as illustrated in the accompanying
drawings, in which like reference characters refer to the same parts throughout the
different figures. The drawings are not necessarily to scale, emphasis instead being
placed upon illustrating the principles of the invention.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The foregoing and other features of the invention will be apparent from the following
more particular description of the invention, as illustrated in the accompanying
drawings, in which like reference characters refer to the same parts throughout the
different figures. The drawings are not necessarily to scale, emphasis instead being
placed upon illustrating the principles of the invention.
Fig. 1 is line representation of fixture 1 and wherein it may be noted that minor changes
with respect to the object of the invention may be present in the cross-sectional view.
Fig. 2 is line representation of Slot Wedge Profile making by Vertical Milling Machine
with the help of Fixture (Item-1) and it may be noted that minor changes with respect to
the object of the invention may be present in the cross-sectional view.
Fig. 3 showing and -Insertion Key 9 at the bottom of the Fixture F.
Fig. 4 a Showing a Tightening Bolt and Slot for holding the Slot wedge.
Fig. 5 Making of Slot Wedge by using the formed fixture on a Vertical Milling Machine.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE
INVENTION
Before describing in detail, special multipurpose fixture for making slot wedges for large
size turbo-generator in accordance with the present invention, it should

be observed that the present invention resides primarily in a novel and non-obvious
combination of hardware elements and method steps. Accordingly, these elements and
steps have been represented by conventional elements and steps in the drawings,
showing only those specific details that are pertinent to the present invention so as not
to obscure the disclosure with details that will be readily apparent to those skilled in the
art having the benefit of the description herein.
The present invention is directed to solve the above-described problems of the prior art
and to provide a method and means for making slot wedges for large size turbo-
generator in accordance with the present invention and to enable to manufacture
accurate slot wedges easily and in short time.
Following steps are used to hold and machine slot wedges using the formed fixture F:
- cut blank 1 for making a fixture F;
- provide a key 9 in fixture F for locking into T-slot of milling machine’s bed;
- cutting a step10 at both end of fixture for holding the fixture by threaded
arrangement;
- provide plurality of threaded holes 4, 5 for proper tightening of fixture F with the
help of threaded arrangement with milling machine’s bed;
- cutting a rectangular slot 8 for putting slot wedge into fixture F;
- provide plurality of threaded hole 2, 3 with threads 6, 7 of adequate size for
tightening slot wedge by using tightening bolt of respective size and to minimize
vibration of slot wedge during machining of slot wedge (job) profile (30-degree
angle) on milling machine;
- Using specific size of packing to maintain the gap between slot wedge and fixture
for different ratings of Turbo-Generator.
Although the present discussion relates to a process for making slot wedges for large
size turbo-generator in accordance with the present invention, more particularly, the
method enables manufacturing of accurate slot wedges without vibration or chatter

marks, it will be appreciated that the device and methods discussed may be readily
adapted for use with other similar procedures. Not only the methods and the tools
devised thereof for quality manufacturing of slot wedges is cheap and easy to
manufacture but also will provide safer and ergonomic means for the operators to deal
with the dismantling and reassembly operation.
It will be appreciated that those skilled in the art will be able to devise various
arrangements that, although not explicitly described or shown herein, embody the
principles of the invention and are included within its scope.
Furthermore, all examples recited herein are principally intended expressly to be only
for pedagogical purposes to aid the reader in understanding the principles of the
invention and the concepts contributed by the inventor(s) to furthering the art and are to
be construed as being without limitation to such specifically recited examples and
conditions. Also, the various embodiments described herein are not necessarily
mutually exclusive, as some embodiments can be combined with one or more other
embodiments to form new embodiments.

WE CLAIM
1. A process for safe manufacturing of improved slot wedges disposed in stators of
large size Turbo-Generator; comprising the steps of:
- cutting a blank 1 for making a fixture F;
- providing an insertion key 9 at the bottom of the in blank of the 1 for locking
into the blank 1 T-slot of milling machine’s bed;
- cutting a step 10 in the blank 1 at both end of the fixture F for holding the
fixture F by threaded means;
- providing a plurality of threaded holes 4, 5 below said step 10 for tightening
of the fixture F with the help of the threaded means at milling machine’s bed;
- cutting a rectangular slot 8 for putting a slot wedge into the fixture F;
- providing a plurality of threaded holes 2, 3 with threads 6, 7 of adequate size
for tightening the slot wedge by tightening bolt of respective size and to
minimize vibration of slot wedge during the machining of slot wedge (job)
profile (30 degree angle) on the milling machine; and
- inserting specific size of packing to maintain the gap between the slot wedge
and the fixture for different ratings of Turbo-Generator.