Mechanical emergency brake for wind turbines and method for operating same

• US 20070189900A1
• Filed: 07/28/2004
• Published: 08/16/2007
• Est. Priority Date: 07/28/2004
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Rogall, Peter, Achenbach, Patrick
• Granted Patent: US 8,007,227 B2
• Time in Patent Office: Days
• US Class Current: 416/132.B
• CPC Class Codes: F03D 7/0224 Adjusting blade pitch
• CPC Class Codes: F03D 7/0248 by mechanical means acting on the power train
• CPC Class Codes: F05B 2260/75 the adjusting mechanism not using auxiliary power sources, e.g. servos
• CPC Class Codes: F05B 2260/76 the adjusting mechanism using auxiliary power sources
• CPC Class Codes: Y02E 10/72 Wind turbines with rotation axis in wind direction

Abstract

A mechanical emergency brake for a wind turbine is provided, said mechanical emergency brake comprising a spiral spring with a loop at its outer end, a cassette for accommodating said spring and a casing for receiving said cassette and said spring, wherein said casing comprises a retention pin to which the loop of the spring can be fixed.

Claims

1. A spiral spring for a mechanical emergency brake of a wind turbine, wherein said spiral spring comprises a fixing means for fixing said spiral spring to a retention means, wherein said fixing means is adapted to rotate about said retention means when being fixed to it.

2. The spring according to claim 1, wherein the fixing means is a loop and said retention means is a retention pin, wherein said loop is formed at an outer end of said spiral spring and said retention pin is an outer retention pin.

3. The spiral spring according to claim 1, wherein said spiral spring comprises a hook for fixing said spiral spring to a drive shaft, wherein said hook is formed at an inner end of said spiral spring and said hook is insertable into a slit formed in said drive shaft.

4. The spiral spring according to claim 1, wherein said spiral spring comprises a further loop for fixing said spiral spring to a retention pin, wherein said further loop is formed at an inner end of said spiral spring and said retention pin is formed on a drive shaft.

5. The spiral spring according to claim 1, wherein said spiral spring is made of texturized steel.

6. The spiral spring according to claim 1, wherein said spiral spring has a thickness in the range of 1.25 mm to 2.25 mm.

7. The spiral spring according to claim 1, wherein said spiral spring has a width in the range of 40 mm to 80 mm.

8. The spiral spring according to claim 1, wherein said spiral spring has a length in the range of 15 m to 30 m.

9. The spiral spring according to claim 1, wherein said spiral spring has a prestress in the range of 50 Nm to 100 Nm, when being wound up in a range of 70% to 90%.

10. A cassette for receiving a spiral spring according to claim 1, said cassette comprising an upper part, a lower part, and separators disposed between said upper and lower parts, wherein said upper and lower parts have a central bore for receiving a drive shaft, and wherein said upper and lower parts further comprise a locking means adapted to receive a retention means.

11. The cassette according to claim 10, wherein said separators are distributed along the periphery of said upper and lower parts.

12. The cassette according to claim 10, wherein the length of said separators is about 1 mm to 3 mm larger than the width of said spiral.

13. The cassette according to claim 10, further comprising guide means provided at the upper and lower parts of the cassette, wherein said guide means are aligned with each other so that they can receive a guide pin.

14. The cassette according to claim 13, wherein said guide means are grooves provided at the periphery of the upper and lower parts of the cassette.

15. The cassette according to claim 13, wherein said guide means are through holes provided in the upper and lower parts of the cassette.

16. The cassette according to claim 10, further comprising at least one further hole provided in the upper part of the cassette.

17. The cassette according to claim 10, further comprising at least one further hole provided in the lower part of the cassette.

18. A spring unit for a mechanical emergency brake of a wind turbine, comprising a spiral spring according to claim 1, and a cassette according to claim 10, wherein said spiral spring is accommodated in said cassette.

19. A casing for a spring energy storage used in a mechanical emergency brake for a wind turbine, comprising a lower wall, a side wall and a top cover, said casing being designed to receive at least one spring unit according to claim 18, wherein said casing further comprises a retention means to which an outer fixing means of a spiral spring can be fixed, and a drive shaft to which an inner fixing means of a spiral spring can be fixed.

20. The casing according to claim 19, wherein said retention means is an outer retention pin for fixing a loop of the spiral spring of said spring unit, said outer retention pin being fixable to said lower wall and to said top cover.

21. The casing according to claim 19, further comprising at least one guide pin being insertable into a guide means of the spring unit.

22. The casing (12) according to claim 19, wherein said casing is oilproof.

23. A spring energy storage for a mechanical emergency brake for a wind turbine comprising a casing according to claim 19 and at least one spring unit according to claim 18, wherein said at least one spring unit is accommodated in said casing.

24. The spring energy storage according to claim 23, wherein 4 to 8 spring units are accommodated in said casing.

25. The spring energy storage according to claim 23, further comprising an oilbath for lubricating said at least one spring.

26. A wind turbine comprising a rotor with at least one rotor blade, a pitch drive for rotating said at least one rotor blade about a longitudinal axis, and a mechanical emergency brake, wherein said mechanical emergency brake comprises a spring energy storage according to claim 23, and wherein said spring energy storage is coupled to a drive shaft of said pitch drive.

27. The wind turbine according to claim 26, further comprising a block against which said rotor blade seats in a feather position.

28. The wind turbine according to claim 27, further comprising a damping element for reducing a longitudinal rotational speed of said rotor blade before seating against said block.

29. The wind turbine according to claim 26, further comprising detecting means for detecting a variable indicative of a holding torque of an electric motor comprised in said pitch drive.

30. The wind turbine according to claim 29, wherein said electric motor is a dc series-characteristic motor and said variable indicative of said holding torque is the motor torque.

31. The wind turbine according to claim 29, wherein said electric motor is a three-phase asynchronous motor and said variable indicative of said holding torque is the active current component.

32. The wind turbine according to claim 29, wherein said detecting means comprise calculating means to calculate the moving average of said variable indicative of said holding torque.

33. The wind turbine according to claim 29, further comprising a memory for storing desired values of said variable indicative of said holding torque, and comparison means for comparing an actual value of said variable indicative of said holding torque with said desired value of said variable.

34. The wind turbine according to claim 33, further comprising reporting means for reporting a faulty condition of said spring energy storage to a wind turbine control, wherein said faulty condition is detectable by said comparison means if said actual value of said variable is lower than said desired value of said variable by a predetermined amount, and wherein said wind turbine control is adapted to shut-down said wind turbine on report of a faulty condition by said reporting means.

35. A method for operating a mechanical emergency brake for a wind turbine, comprising the steps of:

providing a mechanical emergency brake for a wind turbine comprising a spring energy storage;

measuring a variable indicative of a holding torque of a pitch drive motor;

comparing said measured value of said variable with a desired value of said variable;

shutting down said wind turbine if the comparison of said actual with said desired value reveals that the wind turbine is in a fault condition.

36. The method according to claim 35, wherein said pitch drive motor is a dc series-characteristic motor and said variable indicative of said holding torque is the motor torque.

37. The method according to claim 35, wherein said pitch drive motor is a three-phase asynchronous motor and said variable indicative of said holding torque is the active current component.

38. The method according to claim 35, wherein the moving average of said variable indicative of said holding torque is calculated.

39. The method according to claim 38, wherein the moving average is calculated over at least two complete rotations of the rotor.

40. The method according to claim 35, wherein said desired value is determined during the set-up operation of the wind turbine and/or wherein said desired value is obtained from another spring energy storage located at another rotor blade of the wind turbine.

41. A method for operating a mechanical emergency brake for a wind turbine, comprising the steps of;

providing a mechanical emergency brake for a wind turbine comprising a spring energy storage;

detecting the number of rotations of a pitch drive motor after releasing a motor break;

blocking servo converters at a pitch angle between feather and work position;

comparing the detected number of motor rotations with a desired number of motor rotations;

shutting-down the wind turbine if the detected number of motor rotations is smaller than said desired number of motor rotations.

42. The method according to claim 41, wherein said method is accomplished during the start-up of the wind turbine before the wind turbine is connected to the grid.