Field of the invention:
The invention relates to the field of manufacture of stators of hydrogenerators in
general, and to anchoring of the stators with sole plates for hydrogenerators in
particular.
Background and prior art:
The stator is a fabricated structure made of weldable steel plates in which the circular core is built with segmental insulated thin laminations. These laminations are secured at several places throughout the circumference with keys. The stampings have slots in which stator windings are inserted. These stators are anchored on a plurality of sole plates. The anchoring is done to keep the stator in position during the normal course of running and at the time of short circuit conditions which may occur anytime during its operation. The magnitude of torque is very high during short circuit condition as compared to normal operation of generator. The anchoring is therefore provided to withstand stator in position under short circuit conditions also in addition to normal torque.
In prior art, the anchoring was done at site by reaming the holes radially between stator and sole plates. The size of these holes were typically between 30 to 50 mm in diameter and between 150 to 300 mm in length. Dowels were fitted in these holes after sizing them at site as per hole dimensions. These operations were done at site manually by hand tools.
In the prior art , making of reamed holes radially was a very complicated operation because these holes are done in assembled condition in situ where limited space is available. The grinding of dowels were also done at site to suit the size of these holes.

This method had the following major disadvantages:-
• Installation period was very long since all the operations were carried out at site by hand tools manually in situ.
• Various sizes of dowels were required to be made to suit the diameters of holes.
• The rejection rate of dowels was high, hence extra material for dowels was being supplied and transported to site.
• More number of dowels were required at each anchoring place due to limitation of hole size which can be reamed at site by hand tools.
• Additional hand tools were being supplied for site.
The novel anchoring method in accordance with the present invention overcomes the
above limitations of the prior art.
Objects of the invention :-
An object of the invention is to provide the stator anchoring which can be incorporated
during manufacturing of the stator and sole plates at the works itself.
Another objective of the invention is to eliminate manual operations required at site for
anchoring.
A further objective of the invention is to reduce the installation period of the stator
considerably.
Yet another object of the invention is to reduce rejection of dowels made at site.
A still further objective of the invention is to eliminate supply of material and
tools necessary for manual anchoring operation at site.

Description of the inventions:-
In the new method of anchoring according to the invention, the use of radial dowels has
been eliminated fully, hence all operations required for this at site have been avoided. In
this method, rectangular slots are machined in stator as well as in sole plates at
works/factory.
The method in accordance with the invention will be described with the help of the
accompanying drawings.
Brief description of accompanying drawings:-
Fig: 1 shows the plan of stator anchoring in the prior art.
Fig: 2 shows sectional view of assembled dowels in prior art.
Fig: 3 shows the plan of stator anchoring according to the invention.
Fig: 4 shows the details of anchoring according to the invention.
As mentioned earlier most of the preparatory work for the anchoring is completed at the
works to reduce working at site, thereby drastically reducing the installation time.
Rectangular SlOtS in GaCfl SOle plate (Z) and in stator (6) at corresponding locations of
plate are made by machining. The width of slot in sole plate is kept smaller than stator.
Depth is kept almost same in sole plate and stator.
The master anchoring plate (1) is ground to suit the width of slot in sole plate (2) to
ensure 'NO GAP' between sole plate and master anchoring plate. The master anchoring
plate is fitted in the slot of sole plate with the help of screws (3).
Two taper static anchoring plates (4), one on each side of master anchoring plate (1)
are inserted.

Two taper drive anchoring plates (5) are pushed and tightened by hammer in the left
out space in stator slot at both sides of the taper static anchoring plat.
Lastly, retaining plate (7) is fixed with the help of screws (8) on to master anchoring
plate (1) so that taper anchoring plates (static and drive) should not get loosened during
operation of generator.
This method of anchoring has following advantages:-
• The installation time has reduced drastically since no manual machining operation is to be carried out at site.
• Only single size master anchoring plate is adequate.
• Rejection is zero.
• No extra material and hand tools to be supplied to site for manual machining of dowels.
• No grinding of dowels needed at site.

CLAIMS

1. A method of stator anchoring for hydrogenerators comprising the steps of ;
machining of plurality of slots in each of sole plate (2) and stator (6)
corresponding to locations of the sole plates;
grinding the master anchoring plate (1) to suit the width of slot in sole plate
(2) to ensure that there is no gap between the sole plate (2) and master
anchoring plate (1);
fitting the master anchoring plate (1) in each slot of the sole plate (2) with
screws (3);
inserting two taper static anchoring plates (4) on either side of each master
anchoring plate (1);
pushing and tightening by hammer two taper drive anchoring plates (5) in
the remaining space in each stator slot, the taper drive anchoring plates (5)
being positioned on either side of the taper static anchoring plates (4) and
fixing the retaining plate (7) with screws (8) on to the master anchoring
plate (1) so that taper anchoring plates (4, 5) are not loosened during
operation of generators wherein the steps of the method are carried out in
the works so that installation time is drastically reduced.
2. A method of stator anchoring as claimed in claim 1, wherein the depth of the slots in each sole plate (2) and at corresponding location in stator (6) is the same but the width of the slot in sole plate is smaller than the width of the corresponding slot in stator.


3. A method of stator anchoring as claimed in claim 1, wherein the slots in each sole plate and in stator are rectangular slots.

ABSTRACT

METHOD FOR STATOR ANCHORING FOR HYDROGENERATORS

A method of stator anchoring for hydrogenerators comprising the steps of machining of a plurality of slots in each sole plate (2) and in stator (6) corresponding to locations of the sole plate. The master anchoring plate (1) is ground to suit the width of slot in sole plate so that there is no gap between sole plate (2) and master anchoring plate (1). The master anchoring plate (1) is then fitted in the slot of the sole plate (2) with screws (3) when two static anchoring plates (4) are inserted on either side of each master anchoring plates (1) and then two taper drive anchoring plates (5) are pushed and hammered in the remaining space in each stator slot, on either side of the taper static anchoring plates (4) when the retaining plates (7) are fixed on the master anchoring plate (1) with screws (8) so that taper anchoring plates (4, 5) are not loosened during operation of generator.