Method for monitoring demagnetization
View Patent ↗A method for discovering demagnetisation faults of a permanent magnet synchronous generator, such as a wind power generator. The method is performed during operation of the synchronous generator and includes measuring the vibration of the stator, performing a frequency analysis of the vibration, and deducing whether the generator suffers from demagnetization of a permanent magnet, from the vibration analysis. Moreover, geometric eccentricity faults and electric short circuit faults may also be detected from the vibration.
1. A method for monitoring demagnetization of permanent magnets in a synchronous machine, such as a wind power generator, having a stator with windings and a rotor with permanent magnets being arranged to rotate in relation to the stator, the method being performed during operation of the synchronous machine, and the method including the steps of:
measuring with a vibration sensor the vibration of the stator,
performing with an analyzer a frequency analysis of the vibration,
determining with an identifier, on the basis of whether the magnitude of the vibration at the supply frequency of the stator exceeds a threshold value or not, whether the machine suffers from demagnetization of a permanent magnet or not.
2. The method according to claim 1 , wherein the method further comprises the step of: determining, on the basis of whether the magnitude of the vibration at the rotation frequency exceeds a threshold value or not, whether the machine suffers from demagnetization of a permanent magnet or not.
3. The method according to claim 1 , wherein the vibration measurement includes detecting vibrations by means of a vibration sensor that is fixed to a frame of the stator or fixed to the stator.
4. The method according to claim 1 , wherein the machine is a permanent magnet synchronous generator.
5. The method according to claim 1 , wherein the vibration measurement includes detecting vibrations with an accelerometer.
6. The method according to claim 1 , wherein the method is implemented in a control system of a wind power plant.
7. The method according to claim 1 , further comprising the step of presenting an alarm indicating a fault.
8. The method according to claim 1 , wherein the step of determining includes analyzing reference data including magnitude levels corresponding to levels of demagnetization.
9. A system for monitoring demagnetization of permanent magnets in a synchronous machine having a stator with windings and a rotor with permanent magnets being arranged to rotate in relation to the stator, comprising:
a vibration sensor measuring vibration of the stator,
an analyzer performing a frequency analysis of the vibration,
an identifier determining, on the basis of whether the magnitude of the vibration at the supply frequency of the stator exceeds a threshold value or not, whether the machine suffers from demagnetization of a permanent magnet or not.
10. The system according to claim 9 , further comprising a memory having reference data including magnitude levels corresponding to levels of demagnetization.
11. The system according to claim 9 , wherein the identifier confirms a fault indication on the basis of whether the magnitude of the vibration at the rotation frequency exceeds a threshold value or not.
12. The system according to claim 9 , further comprising a display displaying an indication of a fault.
13. The system according to claim 9 , wherein the machine comprises a permanent magnet synchronous generator.
14. The system according to claim 9 , wherein the vibration sensor comprises an accelerometer.
15. The system according to claim 9 , wherein the analyzer is integrated into portable control equipment.
16. The system according to claim 9 , wherein the analyzer is integrated into in a control system of a wind power plant.
17. The method according to claim 1 , wherein the step of determining comprises determining demagnetization from vibrations alone.
18. The method according to claim 8 , wherein the reference data is created by measuring operation using a permanent magnet that is less strong than a nominal magnetic strength normally used.