FORM 2
THE PATENTS ACT, 1970 {39 of 1970) &
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
A METHOD AND SYSTEM FOR REPLACING WIND TURBINE GENERATOR EQUIPMENT;
SUZLON ENERGY LIMITED, A COMPANY INCORPORATED UNDER THE COMPANIES ACT, 1956, WHOSE ADDRESS IS ONE EARTH, OPPOSITE MAGARPATTA CITY, HADAPSAR, PUNE-411 028, MAHARASHTRA, INDIA.
THE FOLLOWING SPECIFICATION
PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

FIELD OF THE INVENTION
The invention relates to wind turbine generators, and more particularly to a method and system for replacing a gearbox of the wind turbine generator. BACKGROUND OF THE INVENTION
Wind turbine generator comprises an assembly of components intended for converting wind driven kinetic energy into mechanical energy. The components include a nacelle, Rotor Shaft, Main Bearing, Gearbox, Generator, Electrical Control Panel and other equipments.
Over the years, wind turbines have experienced a high rate of gearbox breakdown/ failures. Despite reasonable technical advance in quality and reliability of gearboxes, erratic wind trends at different locations often cause gearbox failures.
Generally, these gearboxes are mounted at the nacelle of the windmill at heights ranging from 56 meters to 120 meters from the ground. These gearboxes are usually mounted/dismounted using cranes. Hence during a gearbox failure a crane has to be called to the site/location of the wind turbine to replace or repair the damaged gearbox.
As it is well know, the best locations for installing wind turbine generators are isolated places where the wind is strong and reliable such as coastal areas, at the tops of hills, open plains, gaps in mountains, etc. However access to these isolated places is difficult, especially transporting a crane to such a location for only replacing a gearbox is challenging, time consuming and also expensive.
In view of the above there is a need for a low-cost on-site solution for replacing the gearbox of the wind turbine.

SUMMARY OF THE INVENTION
Accordingly, the present invention in one aspect provides a system for replacing a gearbox of a wind turbine generator, comprising a lifting device having a removable pulley configured for attaching with the gearbox, a transferring system for moving the gearbox in and out of a nacelle of the wind turbine generator and a pulley system for lifting and lowering the gearbox between nacelle and the ground. According to the present invention, the transferring system having a mounting structure having a first beam, and a second beam perpendicular to the first beam installed in the nacelle of the wind turbine generator, a movable pulley assembly mounted on the first beam, the movable pulley assembly configured for coupling with the lifting device for enabling the lifting device to lift or lower the gearbox inside the nacelle, and atleast one beam trolley movably mounted on the second beam near the movable pulley assembly to move the gearbox along a horizontal axis in and out of the nacelle. The pulley system comprises a winch unit having a wire rope wound around a winch drum, a first pulley assembly provided near the base of the tower, a second pulley assembly provided near nacelle of the wind turbine generator and a third pulley assembly mounted on the second beam. The wire rope of the winch unit extends through the first, second and to the third pulley, the third pulley assembly configured for coupling with the pulley provided on the lifting device, thereby enabling lifting and lowering the gearbox. According to the present invention, the beam trolley and the third pulley assembly are positioned such that load of the gearbox can be interchanged between the beam trolley and the third pulley assembly for transferring the gearbox between the transferring system and the pulley system allowing replacement of the gearbox.
According to an embodiment of the present invention, the system further comprises a holding device for locking a main shaft of the wind turbine generator.
In another aspect, the present invention provides a method for replacing a gearbox of a wind turbine generator, the method comprising the steps of locking a main shaft of the wind turbine generator by means of a holding device, disengaging the gearbox, providing a

transferring system in a nacelle of the wind turbine generator for transferring the gearbox in and out of the nacelle, providing a pulley system on the wind turbine generator for lifting and lowering the gearbox between nacelle and the ground, attaching a lifting device to the gearbox, and transferring the decoupled gearbox between the transferring system and the pulley system for lowering and lifting the gearbox of the wind turbine generator thereby replacing the gearbox.
BRIEF DESCRIPTION OF THE DRAWINGS
Reference will be made to embodiments of the invention, examples of which may be illustrated in the accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in the context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figure 1 shows a system for replacing a gearbox of a wind turbine generator in
accordance with an embodiment of the invention.
Figure 2 shows a holding device in accordance with an embodiment of the invention
Figure 3 shows the holding device coupled to a main shaft of the wind turbine generator
in accordance with an embodiment of the invention.
Figure 4 shows a lifting device in accordance with an embodiment of the invention.
Figure 5 shows the lifting device attached to the gearbox in accordance with an
embodiment of the invention.
Figure 6 shows a transferring system in accordance with an embodiment of the
invention.
Figure 7 shows a method for replacing a gearbox of a wind turbine generator in
accordance with an embodiment of the invention, where
Figure 7A shows a method for lowering the gearbox from nacelle of the wind turbine generator; and

Figure 7B shows a method for lifting the gearbox to the nacelle of the wind turbine generator.
DETAILED DESCRIPTION OF THE INVENTION
Various embodiments of the present invention provide a method and system for replacing a gearbox of a wind turbine generator.
A wind turbine generator comprises of a tower; a nacelle coupled towards top of the tower; a gearbox positioned within the nacelle; a plurality of rotor blades, a rotor shaft coupling the rotor blades to the gearbox.
Figure 1 shows a system 100 for replacing a gearbox 102 of a wind-turbine generator 104. The system 100 includes a holding device 200 (shown in figure 2), a lifting device 400 (shown in figure 4), transferring system 110 for moving the gearbox 102 in and out of the nacelle of the wind turbine generator and a pulley system 120 for lifting and lowering the gearbox 102 from the nacelle.
In an embodiment of the invention, the holding device 200 couples and locks the main shaft as shown in figure 3. Advantageously, the holding device 200 prevents rotation of the wind turbine generator and also enables removal of the gearbox 102 without removing the rotor shaft. The holding device 200 as shown in figure 2 has a first holding member 202, a second holding member 204, a first locking member 206 and a second locking member 208. The first holding member 202 and the second holding member 204 extend outwards to form a space to hold the main shaft. In an embodiment of the invention, the first holding member 202 and second holding member 204 are extendable. The first locking member 206 and the second locking member 208 are at the centre, and lock the main shaft of the wind turbine generator. In an embodiment of the invention, the holding device 200 is coupled to the main shaft at all times while replacing the gearbox 102.

On locking the main shaft of the wind turbine generator, the lifting device 400 is attached to the gearbox 102 as shown in figure 5. As shown in figure 4, the lifting device 400 has a first pair of locking members 402, a second pair of locking member 404 and means for adapting a pulley 106 removably. The first pair of locking member 402 and second pair of locking member 404 are perpendicularly coupled to each-other. In an embodiment, each locking member has means 406 for attaching with the gearbox 102. In this regard, the lifting device 400 is attached to the gearbox 102 using D-shackles. Once the lifting device 400 is coupled to the gearbox 102, the gearbox 102 can be lifted and moved using the transferring system 110 and the pulley system 120.
The transferring system 110 enables the gearbox 102 to move in and out of the nacelle. The transferring system 110 as shown in figure 6 includes a mounting structure 112; a movable pulley assembly 114; and at-least one beam trolley 116.
The mounting structure 112 is installed inside the nacelle of the wind turbine generator. According to the present invention the mounting structure 112 is mounted on holding device 400 on one side. The mounting structure has a first beam 112a and a second beam 112b perpendicular to the first beam 112a. The movable pulley assembly 114 is mounted on the first beam 112a for lifting and lowering the gearbox 102 and the beam trolley is mounted on the second beam 112b of the mounting structure for moving in and out the gearbox 102. According to the present invention, the beams of the mounting structure are constructed using l-sections with bolted connections. A person skilled in the art can easily understand erection of the mounting structure from the figures and not required to be described in detail.
The movable pulley assembly 114 mounted on the first beam 112a is configured to couple with the lifting device 400. The movable pulley assembly 114 enables to lift and lower the gearbox 102 with lifting device 400 inside the nacelle.
The beam trolley 116 movably mounted on the second beam 112b is configured to move along a horizontal axis in and out of the nacelle. The beam trolley 116 is configured for

coupling with the gearbox 102 through the lifting device 400. According to the present invention, the beam trolley 116 is mounted near the movable pulley such that the beam trolley 116 can couple with the lifting device 400 lifted by the movable pulley assembly 114. On coupling, the beam trolley 116 with the lifting device 400, the movable pulley assembly 114 is decoupled from the lifting device 400, and the beam trolley 116 is moved towards the second beam 112b.
The pulley assembly 120 as shown in the figure 1 includes a winch unit 122, a first pulley assembly 126 provided near a base of the tower; a second pulley assembly 128 provided near the nacelle of the wind turbine generator; and a third pulley assembly 130 mounted on the second beam 112b of the mounting structure.
The winch unit 122 as shown in the figure .1 is provided on the ground, near the tower. According to the present invention, the winch unit is provided preferably at a distance of 50 meter from the tower. The winch unit 122 has a winch drum (not shown) and a wire rope 124 wound around the winch drum. The wire rope 124 extends from the winch drum through the first pulley assembly, the second pulley assembly, the third pulley assembly and the pulley 106 mounted on the lifting device 400. According to the present invention the winch unit 122 is driven by an electric motor.
The third pulley assembly 130 is configured for coupling with the lifting device 400, wherein the wire rope 124 is also coupled with the lifting device 400. The third pulley assembly 130 is positioned on the second beam 112b such that the load of the gearbox 102 can be interchanged between the beam trolley 116 and the third pulley assembly for transferring the gearbox 102 between the transferring system and the pulley system.
Figure 7A and 7B show a method for replacing a gearbox of a wind turbine generator, where figure 7A shows a method for lowering a gearbox from the nacelle and figure 7B shows a method for lifting the gearbox to the nacelle of the wind turbine generator.

As shown in figure 7A, the method for lowering the gearbox for replacing the gearbox comprises the steps of S702 for locking a main shaft of the wind turbine generator by means of a holding device. At S704 a transferring system is provided or installed in a nacelle for transferring the gearbox in and out of the nacelle. According to the present invention, installing the transferring system includes installing a mounting structure in the nacelle, mounting a movable pulley assembly and a beam trolley on the mounting structure. The mounting structure comprises a first beam and a second beam perpendicular to the first beam. According to the present invention, movable pulley assembly is mounted on the first beam and the beam trolley is preferably mounted on the second beam.
According to the present invention, at S706 a pulley system is provided or installed on the wind turbine generator for lifting and lowering the gearbox between nacelle and the ground. According to the present invention, installing the pulley system includes mounting a winch unit on the ground near the tower; mounting a first pulley assembly near base of the tower; mounting a second pulley assembly near the nacelle of the tower; mounting a third pulley assembly on the second beam of the transferring system; and guiding a wire rope extends from the first pulley assembly, the second pulley assembly and to the third pulley though the pulley adapted on the lifting device.
At S708 the gearbox is disengaged and subsequently at S710 a lifting device is attached to the gearbox. Once the lifting device is attached to the gearbox at S712 a movable pulley assembly is coupled to the lifting device, and at S714 the gearbox is lifted by means of the movable pulley assembly coupled to the lifting device. Once the gearbox is lifted by the movable pulley assembly, at S716 the lifting device is coupled to a beam trolley for moving the gearbox out of the nacelle, and at S718 gearbox is transferred between the beam troiley and a third pulley assembly for lowering the gearbox from the nacelle of the wind turbine generator, wherein transferring the gear box includes coupling the third pulley assembly with the lifting device, transferring load of the gearbox to the third pulley assembly from the beam trolley and

decoupling the beam trolley. On transferring the gearbox to the third pulley assembly, the winch unit is driven and the gearbox is lowered to the ground at step S720.
On coupling the third pulley assembly to the lifting device, lifted to the nacelle by means of the third pulley assembly coupled to the lifting device.
Similarly, the gearbox can be lifted from the ground using the lifting device, and then installed in the nacelle. In this regard on lowering the gearbox, the gearbox may be inspected onsite, and accordingly a maintenance operation can be carried out or a new gearbox can be lifted to the nacelle.
Figure 7B shows a method for lifting the gearbox to the nacelle from step S722 by attaching the lifting device to a replaced gearbox. At S724 the third pulley assembly is coupled to the lifting device at S724. On coupling the third pulley assembly to the lifting device, the winch unit is driven and at S726 the gearbox is lifted to the nacelle by means of the third pulley assembly coupled to the lifting device. The gearbox on reaching the nacelle, at S728 the gearbox is transferred between the third pulley assembly of the pulley system and the beam trolley of the transferring system for moving the gearbox inside the nacelle of the wind turbine generator, wherein transferring the gearbox includes the step of coupling the beam trolley with the lifting device, transferring load of the gearbox to the beam trolley from the third pulley assembly and decoupling the third pulley assembly. Further, at S730 gearbox is coupled to the movable pulley assembly and at S732 the gearbox is lowered and installed in the nacelle.
Advantageously, the present invention provides an on-site solution for replacing wind turbine generator equipment obviating from the tedious process of transporting a crane to the site of the wind-turbine generator especially to replace equipment such as gearbox of wind-turbine generator, thereby saving on cost and time involved in replacing wind-turbine equipment.

WE CLAIM:
1. A system for replacing a gearbox of a wind turbine generator, the system comprising: a fitting device configured for attaching with the gearbox, said lifting device having a pulley adapted removably;
a transferring system for moving the gearbox in and out of a nacelle of the wind turbine generator, the transferring system having:
a mounting structure installed in the nacelle of the wind turbine generator, the mounting structure having a first beam, and a second beam perpendicular to the first beam;
a movable pulley assembly mounted on the first beam, the movable pulley assembly configured for coupling with the lifting device, the movable pulley assembly enabling the lifting device to lift or lower the gearbox inside the nacelle; and
at-least one beam trolley movably mounted on the second beam near the movable pulley assembly to move the gearbox along a horizontal axis in and out of the nacelle, the beam trolley being configured for coupling with the lifting device; and a pulley system for lifting and lowering the gearbox between nacelle and the ground, the pulley system having:
a winch unit having a wire rope wound around a winch drum;
a first pulley assembly provided near the base of the tower;
a second pulley assembly provided near nacelle of the wind turbine generator; and
a third pulley assembly mounted on the second beam, the wire rope extends through the first pulley assembly, the second pulley assembly and to the third pulley assembly through the pulley provided on the lifting device, the third pulley assembly

configured for coupling with the lifting device, thereby enabling lifting and lowering the
gearbox;
wherein, the beam trolley and the third pulley assembly are positioned such that load of
the gearbox can be interchanged between the beam trolley and the third pulley
assembly for transferring the gearbox between the transferring system and the pulley
system allowing replacement of the gearbox.
2. The system as claimed in claim 1, wherein the system further comprises a holding device for locking a main shaft of the wind turbine generator.
3. The system as claimed in claim 1, wherein the lifting device comprises a first pair of locking members and a second pair of locking members perpendicularly coupled to the first pair of locking members, each locking member has means for coupling with the gear box.
4. A method for replacing a gearbox of a wind turbine generator, the method comprising the steps of:
locking a main shaft of the wind turbine generator by means of a holding device;
providing a transferring system in a nacelle of the wind turbine generator for transferring the gearbox in and out of the nacelle;
providing a pulley system on the wind turbine generator for lifting and lowering the gearbox between nacelle and the ground;
disengaging the gearbox;
attaching a lifting device to the gearbox; and
transferring the decoupled gearbox between the transferring system and the pulley system for lowering and lifting the gearbox of the wind turbine generator thereby replacing the gearbox.
5. The method as claimed in claim 4, wherein the step of providing the transferring system
includes the step of

installing a mounting structure in the nacelle, the mounting structure having a first beam and a second beam perpendicular to the second beam;
mounting a movable pulley assembly on the first beam for lifting or lowering the gearbox in the nacelle; and
mounting a beam trolley on the second beam for moving the gearbox in and out the nacelle.
6. The method as claimed in claim 4, wherein the step of providing the pulley system
includes the step of:
mounting a winch unit on the ground near the tower; mounting a first pulley assembly near base of the tower; mounting a second pulley assembly near the nacelle of the tower; mounting a third pulley assembly on the second beam of the transferring system; and
extending a wire rope from the first pulley assembly, second pulley assembly to the third pulley through the pulley provided on the lifting device .
7. The method as claimed in any of the preceding claims, wherein lowering the gearbox
includes the step of
coupling the movable pulley assembly to the lifting device;
lifting the gearbox by means of the movable pulley assembly coupled to the lifting device;
coupling the lifting device to the beam trolley for moving the gearbox out of the nacelle; and
transferring the gear box between the beam trolley to the third pulley assembly for lowering the gearbox from the nacelle of the wind turbine generator, wherein transferring the gear box includes coupling the third pulley assembly with the lifting

device, transferring load of the gearbox to the third pulley assembly from the beam trolley and decoupling the beam trolley.
8. The method as claimed in any of the preceding claims, wherein lifting the gearbox includes the step of
coupling the third pulley assembly to the lifting device;
lifting the gearbox to the nacelle by means of the third pulley assembly coupled to the lifting device; and
transferring the gear box between the third pulley assembly of the transferring system and the beam trolley of the pulley system for moving the gearbox inside the wind turbine generator, wherein transferring the gearbox includes coupling the beam trolley with the lifting device, transferring load of the gearbox to the beam trolley from the third pulley assembly and decoupling the third pulley assembly.