FIELD OF INVENTION
The present invention relates to a fixture to protect stator core from direct
heating during welding the stator core bars in turbo generators.
BACKGROUND OF INVENTION
Large Capacity turbo generators are cylindrical machines with uniform air gap.
The stator of the generators is made of laminated sheets. The laminations are
stacked one above the other to form active length of the machine. The insulating
bolts passed through hold the stator core laminations together. The insulating
bolts are bolted on both ends to the press plate. The outer periphery of the
stator core is provided with number of core bars. These core bars are welded to
the press plate and the spring basket. The stator core laminations have
insulation coating of their surface. While welding the core bars to the press plate
and spring basket it is observed that direct heat due to welding spatters is
damaging the core.

This invention specifically applicable to turbo Generator module
THDF - 600/660 MW. In the workshop while welding the core bars to the press
plate and spring baskets, it is observed that the stack of laminated stator core is
prone to get damaged due to the impact of the welding spatters directly on the
core. In this work the terminology of core bar is used instead of key bar. A
fixture along with shield is designed to protect the core from direct heat and
localized damage due to welding.
OBJECTS OF THE INVENTION
Therefore it is an object of the invention to propose a fixture to protect stator
core from direct heating during welding the stator core bars in turbo generators
which is capable of preventing the localized heating and possible damage of the
core due to welding spatters.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Fig.l- Shows an end view (1A), top view (1B) and isometric view (1C) of
the fixture according to the invention and details A(1D) of 1A.

Fig.2- Shows the perspective view of the shield.
Fig.3- Shows the view of the slot bar module designed in accordance with
the present invention.
Fig.4- Shows an isometric view of the fixture according to the invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
The fixture (1) along with a shield (2) with sliding mechanism fixed
on it is used during assembly to protect the core (8) from direct heating due to
welding.
The stator core (8) assembly comprises laminated core mounted
vertically adopted to form stack of the stator core, provided with insulating bolts
bolted to press plate (11), and number of core bars (9) having length more than
the height of the stacked laminations. The core assembly further comprises core
bars (9) welded to the press plate (11) and the spring baskets bars (10). While
welding the stator core (8) is prone to localized damage due to direct heating. A
fixture (1) with shield (2) is designed to protect the stator core (8) from direct
heating during the welding process.

In accordance with a first aspect of the present invention, a fixture
is provided comprising of a structural element which can be mounted on the
press plate (11) as well as spring basket bars (10) while welding the core bars
(9). The fixture is provided with fixing bolts (5B, 6B) so that the height of the
fixture can be adjusted while mounted on a vertical reference base. The fixture
element is provided with a slot groove (4) to provide flexible path for the
shielding plate (2) to move in horizontal direction either ways left and right. The
grove (4) acts as a recess for receiving another structural element coupled to the
shield.
In accordance with the second aspect of the present invention, a
shield sheet (2) is provided which is adapted to be mounted in vertical position
along with a T shaped slot Bar (3). The shielding plate (2) resists the high
temperature limits due to the welding spatters.
In accordance with the third aspect of the present invention, a T-
Shaped slot bar (3) is provided which is adapted to be mounted in horizontal
position on the shield plate (2). The T-shaped slot bar is mounted on the shield

with the help of screws (7A). The receiving member groove (4) in the fixture (1)
receives the T-Shaped slot bar (3) along with the shield (2) and holes (7B) of the
shield .
The fixture assembly comprising of fixture (1), fixture bolts (5B,
6B), shield plate (2), T-Shaped slot bar (3) mounted horizontally on the press
plate as well as spring basket bars (10) while welding the core bars. The features
are adjustable height, sliding mechanism of the shield plate, less weight, easy to
handle, ease of manufacturing.
The shielding plate element (2) is mounted in vertical position with
the help of a groove (4) onto the fixture. The shielding element is provided with
holes (7B). These holes can be circular and also of tapered nature so that the
shielding plate (2) can be displaced vertically.
Along with the shield plate element (2), a Slot bar (3) structural
element is mounted onto the bottom side of shielding element (2) in a horizontal
position, This slot bar (3) structural element is equal or less than the width of the
shielding element.

A slot groove (4) provided in the fixture, T-shape which acts as a
recess to carry the slot bar structural element.
A locking pin (5A) is provided on the top surface of the fixture.
After placing the shielding plate (2A), at the desired position the locking pin (5A)
is tightened so that the shielding plate (2) along with the slot bar (3) are
restrained from the movement.
A locking grove (6A) is provided on the top surface of the fixture.
Which acts as a recess to carry the locking pin (5A).
Fixing Bolts (5B, 6B) are provided on the fixture. These bolts are
such that the alignment of the fixture is adjusted in the vertical position. By
tightening and loosening the bolts the fixture can be moved vertically upwards
and also downwards. Such an arrangement is provided to avoid any fouling with
the local objects on the press plate or spring basket.
The fixture (1) with shield plate (2) having sliding mechanism fixed
on it is mounted either on stator press plate (11) or spring basket bars (10). The
fixture (1) is of 'c' shaped structure and made of mild steel either fabricated of
milled into a single unit.

WE CLAIM
1. A fixture to protect stator core from direct heating during welding the
stator core bars in turbo generators of 600/660 MW comprising;
- a 'c' shaped structure having a base (4A) and a top (4B) joined by
a vertical plate (4C);
- a plurality of bolts (5B, 6B) on the top and bottom surface of the
fixture for mounting it on the stator press plate (11) or spring
basket bars (10);
Characterized in that,
- a shield plate (2) which can slide is fixed in the grooves/T-slots (4)
of the fixture at the top for protecting the stator core (8) from
direct heat due to welding and thus for preventing damage of the
core (8).
2. A fixture as claimed in claim 1, wherein the fixture is mounted on the
stator press plate (11) or spring basket bars (10) with the bolts (5B, 6B).

3. A fixture as claimed in claim 1, wherein the fixture (1) has T-slot (4) for
accommodating T-shaped slot bar (3).
4. A fixture as claimed in claim 1, wherein the T-slot bar (3) is provided in
the T-slots (4) of the fixture (1).
5. A fixture as claimed in claim 1, wherein the shield plate (2) is fixed with
the T-slot bar (3) by screw (7A).

ABSTRACT

A fixture (1) of 'c' shaped structure having a base (4A) and a top (4B) jointed
by vertical plate (4C) is made either by fabrication or milled to a single unit.
The fixture has T-shaped slot (4) to provide T-slot bar (3) in the groove. A
shield plate (2) is fixed to the T-slot bar (3) with screw (7A). The shield,
which can slide is provided in the fixture (1) to protect the stator core from
direct heating due to welding.