FIELD OF INVENTION
The invention relates to an improved fixing arrangement of axial fan used in hydrogenerators
arresting transferring of the centrifugal force on to rim end plate.
BACKGROUND OF THE INVENTION
The axial fans are fixed at top and bottom of rotor rim to generate the air flow in
hydrogenerator for cooling the stator and rotor. As the rotor rotates these fans, circulate air
through poles, stator core and winding which in turns cools the hot parts of hydrogenerator.
In prior art, the axial fans are fixed directly on rotor rim end plate. The rotor rim end plates
are assembled on top and bottom of rim assembly. The rim assembly is made with thin
laminations of high tensile steel. The rim assembly is friction held and is designed in such a
way that frictional force between rim end plates and punching is more than centrifugal force
for rim end plate. As axial fan are fixed directly on rim end plates, the centrifugal force of
axial fans also added on rim end plate. This results a higher risk of accident due to this

additional centrifugal force. Due to this, frictional force between punching and rim end plate
has to be increased to overcome centrifugal force of rim end plate along with axial fan.
Therefore more tightening pressure required to generate this frictional force and large size
rim studs are used. The fixing arrangement of axial fans in prior art is shown in figure 1(A)
and 1(B). The prior fixing arrangement of axial fans has following disadvantages.
1. Rotor rim has to be tightened at higher pressure to overcome additional
centrifugal force of axial fans. Therefore, size of clamping arrangement (studs,
nuts etc) has increased considerably, hence higher cost.
2. Cost of tightening equipment increases due to increased capacity.
3. Risk of accident was higher due to additional centrifugal force.
In view of above, an improved fixing arrangement of axial fans without transferring the
centrifugal force of axial fan on rim end plate has been explored and invented without
sacrificing the performance of hydrogenerator.
OBJECTS OF THE INVENTION
Therefore it is an object of the invention to propose an improved fixing arrangement of axial
fan for hydrogenerator, which is capable of arresting the transferring of the centrifugal force
on to the rim end plate.

Another object of the invention is to propose an improved fixing arrangement of axial fan for
hydrogenerator, which is economical.
A further object of the invention is to propose an improved fixing arrangement of axial fan
for hydrogenerator, which is capable of reducing the risk of accident.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention can be described in detail with the help of the figures in accompanying
drawings.
Figure 1(A) fixing arrangement of axial fans in prior art.
Figure 1(B) showing enlarge details of fixing arrangement of axial fans in prior art.
Figure 2(A) invented improved fixing arrangement of axial fans.
Figure 2(B) showing section AA of invented improved fixing arrangement of axial fans.
Figure 2 (C) showing enlarged details of invented fixing arrangement of axial fans.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
OF THE INVENTION
In prior art the axial fans (6) are fixed on rim end plate (1) with the help of fitted bush (5),
rim stud (3), nut (4) and locking plate (2) as shown in figures 1A and 1B. When rotor
rotates, additional centrifugal force of axial fans comes on rotor rim end plate (1) through
fitted bush (5). The rim studs (3) are tightened by nuts (4) and gives higher frictional force
between rim punchings and rim end plate so that rim punching (7) should not slip during
operation. Thus, in this case rim stud size and tightening equipments size are higher to
achieve required additional frictional force of axial fans.
In invented design as shown in Figure 2(A), 2(B) and 2(C), the fixing arrangement of axial
fan segment (6) are made in such a way that centrifugal force of axial fans does not come
on rim end plate (1). All centrifugal force of axial fans comes on rotor rim stud (3). In this
invented arrangement special collar nut (9) and fitted bush (8) has been provided. During
assembly, collar nut (9) tightened on rim stud (3) then axial fan segment (6) placed on rim
end plate, after that fitted bush (8) placed and welded on fan segment bottom plate. Then
this assembly is tightened with help of nut (4) and washer (10). The washer (10) is welded
with fitted bush (8). Finally, rim nut (4) is locked by locking bar (11). In this invented

assembly, when rotor is rotated, the centrifugal force of axial fan is transferred directly on
rim stud (3) with the help of fitted bush (8) and collar nut (9) since the fitted bush is welded
on to bottom plate of fan segment. Thus frictional force requirement between rim end plate
(1) and rim punching (7) decreases to a high extent and rim stud and tightening equipment
size decreases considerably.
The invention of improved fixing arrangement of axial fans has resulted following
advantages:
1. Centrifugal force of axial fans are directly comes on rim stud. Therefore, size of clamping
arrangement (studs, nuts, washers etc) has been decreased.
2. Cost of tightening equipment decreases.
3. Risk of accident reduces.
4. There is cost reduction about 15% due to reduction in material of rim studs and nuts and
reduction in cost of tightening equipment.

WE CLAIM
1. An improved fixing arrangement of axial fan for hydrogenerator arresting the
transferring of the centrifugal force on to rim end plate comprising:
- disposing axial fan segment (6) on the rim end plate (1);
- placing the rim end plate (1) on the rim punching (7);
- tightening the collar nut (9) on the rim stud (3);
characterized in that,
a fitted bush (8) is placed and welded on fan segment bottom plate (12) when the
assembly of bush (8) and plate (12) is tightened with the help of nut (4) and washer
(10), wherein the washer (10) is welded with fitted bush (8) to transfer the centrifugal
force of axial fan directly on rim stud (3) through fitted bush (8) and collar nut (9).
2. An improved fixing arrangement of axial fan as claimed in claim 1, wherein the locking
bar (11) locks the rim nut (4).

An improved fixing arrangement of axial fan for hydrogenerator arresting the transferring of
the centrifugal force on to rim end plate comprises by disposing axial fan segment (6) on the
rim end plate (1) when the collar nut is tightened on the rim stud. The fitted bush (8) is
placed and welded on fan segment bottom plate (12) and this assembly of bush (8) and
plate (12) is tightened with the help of nut (4) and washer (10) wherein the washer (10) is
welded with fitted bush (8) so that the centrifugal force of axial fan is transferred directly on
rim stud (3) with the help of fitted bush (8) and collar nut (9).