Title of Invention

"A SAFETY DEVICE AGAINST TORQUE ARM DAMAGE IN A WIND ELECTRIC GENERATOR"

Abstract The invention relates to a safety device against damages of torque arm, which in turn eliminate breakage of flexible coupling, disc spring etc. in a wind electric generator comprising rotor blades (1) with hub (2) and nose cones (3), connected to bearing housing (4) and shaft (5) having a disc brake (7) with brake caliper (6) and connected to the gear box (8) mounted on the main shaft (5) the input of the said gear box (8) is connected to the generator (10) through a flexible coupling (9) and supported at two ends by bracket arrangement (21), Rod - end bearing (22), torque-arm (23) and all the said components are mounted on structure of the nacelle (13) wherein vibration sensor (19) and vibration sensor weight provided near the generator (10) on the structure of the nacelle (13) and deflection sensor (18) provided below the gear box (8) between the springs (25) and the bracket (26) and connected in parallel to the vibration sensor providing a signal to the controller to stop the machine when the tilt exceeds beyond the adjustable set value.
Full Text This invention relates to a safety device against damages of torque-arm, which in turn eliminate breakage of flexible coupling, disc spring etc. in a wind electric generator.
In a horizontal axis wind electric generator, the major components are mounted on a base frame known as nacelle. The gear box of step up type is generally mounted on to the main shaft.
One of the main disadvantages with the present system is that the gear box is hanging on to the main shaft without any base support with the nacelle. The support of the gear box on the main shaft does not pass through the center of gravity of the gear box and the gear box would be tilting down on one side and would not remain horizontal.
Yet another disadvantage with the present system is that the rotating gears in the gear box would have reaction on to the gear box body which would try to rotate the body.
Therefore the main object of the present invention is to propose a novel and innovative safety device in a wind generator, which does not allow the tilt of the gear box to go beyond the combined effects of the elastic limit of the torque-arm rod end and the spring compressive limit. The systems will stop the machine if the tilt exceeds beyond an adjustable set value thus ensuring the safety of the flexible coupling and the torque-arm in a wind electric generator.
Another object of the present invention at a safety device in a wind generator is that it is based on the modification of the vibration sensor, to be used as a deflection sensor.
Yet another object of the present invention of a safety device in a wind generator is to adapt it in the existing software of the controller.
Further object of the present invention of a safety device in a wind generator is to make it 100% reliable.
According to the present invention there is provided a safety device against torque-arm damage in a wind electric generator comprising rotor blades with hub and nose cone, connected to bearing housing and shaft having a disc brake with brake caliper and connected to the gear box mounted on the main shaft, the input of the said gear box is connected to the generator through a flexible coupling and supported at two ends by bracket arrangement, Rod - end bearing, torque-arms and all the said components are mounted on structure of the nacelle characterized by vibration sensor and vibration sensor weight provided near the generator on the structure of the nacelle and deflection sensor provided below the gear box between the springs and the bracket and connected in parallel to the vibration sensor providing a signal to the controller to stop the machine when the tilt exceeds beyond adjustable set value.
The nature of the invention, its objective and further advantages residing in the same will be apparent from the following description made with reference to non-limiting exemplary embodiments of the invention represented with reference to the accompanying drawings.
Figure 1 - schematic drawing of a wind generator
Figure 2 - Nacelle assembly
Figure 3 - Arrangement of the gear box support.
In accordance with the present invention in a horizontal axis wind electric generator, the major components such as blades (1), hub (2), nose cone (3), bearing housing (4), main shaft (5), mechanical brake (6, 7) gear box (8), flexible coupling (9), generator (10), Yaw drive (11), etc. are mounted on a bull gear (12) and tower (15). The rotor consisting of blades (1), hub (2), and nose cone (3), extracts kinetic energy in the wind and converts it into rotary motion of the shaft, which is about 40 rpm for a typical 250 KW wind electric generator. The step-up gear box increases this rpm to a higher value of about 1000 rpm, to match with the rpm of the electric generator (10) which converts rotary motion of the shaft into electrical energy.
There is a disc brake (7) with brake caliper (6) mounted on the main shaft (5):
A bull gear (12) mounted on to the nacelle structure (13) and fixed on to the tower (15). The entire above assembly is provided with a nacelle cover (14).
GEAR BOX
Most wind electric generators use gear box (8), which is of step-up type in which the input rpm of the shaft is lower, and the output rpm of the shaft is higher. The gear box (8) is generally with hollow shaft and is mounted on to the main shaft (5). This is done for two reasons. One to reduce the overall length of the system and another to reduce the number of components to be fixed on to the nacelle (13) to have lesser problems of their alignment. Thus, the gear box (8) is hanging onto the main shaft (5) without any base support with the nacelle (13),,
To avoid the tilting or rotation of the gear box (8), supports are provided on two sides of the gear box (8). This support system consists of various components such as bracket (21) on gear box body rod - end bearing (22), torque-arm (23) with threaded ends nuts and lock nuts (24) shock absorbing disc springs (25), and support bracket (26) fixed to the nacelle (13). The provision of disc springs (25) allows the gear box (8) to absorb shock loads with minimum of stresses. This also provides for marginal tilting motion of the gear box (8).
The output shaft of the gear box (8) is connected to the electric generator (10) through a flexible coupling (9). This coupling (9) transmits the rotating shaft power of the gear box (8) to the generator (10) shaft. This flexible coupling (9) is capable of taking care of mis-alignment of the two shafts. This misalignment may arise due to the misalignment of generator shaft with respect to the gear box shaft during assembly of the generator (10) to the nacelle base. It should be noted that gear box (8) is hanging to the main shaft (5) and is not fixed to the nacelle (13) base. The misalignment also arises during operation, since the gear box (8) is allowed to tile marginally due to forces coming on to it, as mentioned earlier, and the generator (9) is fixed to nacelle (13).
In principle, this system should work satisfactory, however, on several occasions it has been observed that the torque-arm (23) have broken causing the flexible coupling (9) to damage completely and the gear box (8) to tilt excessively. Damage to the torque-arms (23) rod implies that some sudden excessive load is coming on to the torque-arm (23) which is causing elongation (or compression) of the torque-arm (23) beyond the elastic limit of the arm. This also implies that the tilt of gear box (8) is beyond the combined effect of elastic limit and the compression limit of the disc spring (25). This sudden excessive load may be due to various causes such as
(a) sudden gusty wind which causes sudden heavy load (it should
be noted that power in the wind is proportional to cube of the
wind velocity i.e. doubling the wind increases the power by eight
times, which is a very high sudden load)
(b) system resonance
(c) mal-functioning of the controller
(d) fatigue loading
(e) springs becoming insufficient due to loading property with aging
or damage
(f) loosening of nuts etc.
Once the torque-arm rod (23) damages, it is no more able to hold the gear box (8) in position, causes it to tilt excessively and damaging the flexible coupling (9). Each such damage causes a loss at minimum of Rs. One Lakh.
DESCRIPTION OF NOVEL SYSTEM
The novel system refers to limiting the tilt of the gear box (8) within the limit beyond which this torque-arm (23) breaks. This is to be done through a deflection sensor (18) which is to be provided below the gear box (8) at the location as shown in figure 3. The location of the deflection sensor (18) is also shown in Figure 2. This deflection sensor (18) as suggested, is a modified form of a vibration sensor (19) available in the market and is generally provided in a wind electric generator (10) to limit the vibration of the nacelle (13). The vibration sensor (19) location is shown in figure 2.
The location of the weight (20) on the wire in the vibration sensor (19) is adjustable and die wire to which it is attached if flexible and is capable of bending. The vibration sensor (19) is put at the end of the nacelle (13) where the vibration is expected to be maximum. Due to vibration of the nacelle (13), the weight (20) of the vibration sensor (19) oscillates, causing the wire to deflect. If the deflection goes beyond a set limit, the machine stops.
The present suggestion refers to the use of deflection, sensor (18) as a modified form of vibration sensor (19) instead of vibration sensor (19), with the following modifications.
1. The wire (flexible) in the vibration sensor is to be replaced by a
rod (non-flexible)
2. Weight is not required
3. The fixing base with round holed in the vibration sensor is to be changed
to elongated holes, in the deflection sensor, so that the height location of the
deflection sensor is adjustable. This is required to adjust the gap between the
gear box and the deflection sensor rod.
4. The location of the deflection sensor (18), on the nacelle (13) is near
and below the gear box (8) base (Figure 3) and not at the end of the nacelle
(13) as in vibration sensor (19).
The gear box (8) in normal operation, tilt due to variable loads caused by fluctuating nature of wind and consequently giving variable power generation. During normal operation the tilt is within permissible limits, as allowed by the torque-arm (23) and the springs (25), and the machine runs safely. However, due to various abnormal causes, as mentioned earlier, this tilt sometimes goes beyond the permissible limits, causing the torque-arm (23) and consequently the flexible coupling (9) to break. The present invention of a deflection sensor (18), a modified form of a vibration sensor (19) would not allow the tilt to go beyond the permissible limit. In that eventuality the deflection sensor (18) would send a signal to the controller which would stop the machine.
The deflection sensor (18) may be connected in parallel to the vibration sensor (19), so that no change in the software of the controller logic is required.
The invention described hereinabove is in relation to a non-limiting embodiment and as defined by the accompanying claims.



WE CLAIM
1. A safety device against damages of torque-arm which in turn eliminates breakage of flexible coupling, disc spring, etc. in a wind electric generator comprising rotor blades (1) with hub (2) and nose-cone (3), connected to bearing housing (4) and shaft (5) having a disc brake (7) with brake caliper (6) and connected to the gear box (8) mounted on the main shaft (5) the input of the said gear box (8) is connected to the generator (10) through a flexible coupling (9) and supported at two ends by bracket arrangement (21), Rod-end bearing (22), torque-arms (23) and all the said components are mounted on structure of the nacelle (13) characterized by vibration sensor (19) and vibration sensor weight provided near the generator (10) on the structure of the nacelle (13) and deflection sensor (18) provided below the gear box (8) between the springs (25) and the bracket (26) and connected in parallel to the vibration sensor providing a signal to the controller to stop the machine when the tilt exceeds beyond adjustable set value.
2. A safety device as claimed in claim 1 wherein the said gear box (8) is mounted on the main shaft (16) with supports provided on two sides of the said gear box (8) and the said supports comprises of brackets (21) and mounted on rod-end bearings (22), torque-arm (23) with threaded ends and fixed with nuts (24) over disc springs (25) and the said disc springs are mounted on a bracket (26) on nacelle and entire assembly is mounted on a brake (7) on nacelle (13).
3. A safety device as claimed in claim wherein a deflection sensor (18) is provided to limit the vibration of the nacelle (13).
4. A safety device as claimed in claim 1 wherein the said vibration sensor
(19) with a vibration sensor weight (20) provided at the end of the nacelle
(13) and attached to an adjustable wire.
5. A safety device as claimed in claim 1 wherein the said deflection sensor
(18) is connected in parallel to the vibration sensor (19) providing a signal to
the controller.
A safety device against torque-arm damage in a wind electric generator
as herein described and illustrated with reference to the accompanying
drawings.

Documents:

3418-del-1997-abstract.pdf

3418-del-1997-claims.pdf

3418-del-1997-correspondence-others.pdf

3418-del-1997-correspondence-po.pdf

3418-del-1997-description (complete).pdf

3418-del-1997-drawings.pdf

3418-del-1997-form-1.pdf

3418-del-1997-form-18.pdf

3418-del-1997-form-19.pdf

3418-del-1997-form-2.pdf

3418-del-1997-form-3.pdf

3418-del-1997-gpa.pdf


Patent Number 214873
Indian Patent Application Number 3418/DEL/1997
PG Journal Number 10/2008
Publication Date 07-Mar-2008
Grant Date 18-Feb-2008
Date of Filing 27-Nov-1997
Name of Patentee BHARAT HEAVY ELECTRICALS LTD.
Applicant Address BHEL HOUSE, SIRI FORT, NEW DELHI-110049, INDIA.
Inventors:
# Inventor's Name Inventor's Address
1 DR. RAMESH PITAMBAR GUPTA BHARAT HEAVY ELECTRICALS LTD., CORP. R & D DIVISION VIKASNAGAR, HYDERABAD-500093, INDIA.
PCT International Classification Number A61B 19/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA