Non-Invasive monitoring and diagnosis of electric machines by measuring external flux density

• US 20090243647A1
• Filed: 03/31/2008
• Published: 10/01/2009
• Est. Priority Date: 03/31/2008
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Salem, Sameh Ramadan, Salon, Sheppard, Chari, Madabushi Venkatakrishnama, Kwon, O-Mun
• Granted Patent: US 7,880,473 B2
• Time in Patent Office: Days
• US Class Current: 324/765.10
• CPC Class Codes: G01R 31/343 in operation
• CPC Class Codes: H02P 29/0241 the fault being an overvoltage

Abstract

System and methods for monitoring electric machines are provided. A magnetic field associated with the electric machine is measured at one or more points external to the electric machine, wherein a respective magnetic field value is associated with each of the one or more points. The one or more measured magnetic field values are compared to one or more corresponding expected values, and a determination of whether a fault is present in the electric machine is made based at least in part on the comparison.

Claims

1. A method for monitoring an electric machine, comprising:

measuring a magnetic field associated with the electric machine at one or more points external to the electric machine, wherein a respective magnetic field value is associated with each of the one or more points;

comparing the one or more measured magnetic field values to one or more corresponding expected values; and

determining, based at least in part on the comparison, whether a fault is present in the electric machine.

2. The method of claim 1, wherein measuring a magnetic field at one or more points external to the electric machine comprises measuring a magnetic field at a plurality of points external to the electric machine, and the method further comprising:

determining a combined value of the magnetic field based at least in part on the plurality of measurements,

wherein comparing the one or more magnetic field values to one or more corresponding expected values comprises comparing the determined combined value to an expected combined value.

3. The method of claim 2, wherein determining a combined value of the magnetic field based at least in part on the plurality of measurements comprises determined a combined value based at least in part on an integration of the plurality of measurements.

4. The method of claim 1, wherein comparing the one or more measured magnetic field values to one or more corresponding expected values comprises comparing the one or more measured magnetic field values to one or more corresponding ranges of expected values.

5. The method of claim 1, wherein if a fault is determined to be present, the method further comprises:

identifying a fault type associated with the fault based at least in part on comparing the one or more measured magnetic field values to one or more corresponding expected values associated with the fault type.

6. The method of claim 1, wherein measuring a magnetic field associated with the electric machine comprises measuring a magnetic field while the electric machine is online.

7. The method of claim 1, wherein measuring a magnetic field associated with the electric machine at one or more points external to the electric machine comprises measuring the magnetic field utilizing one or more magnetometers corresponding to the one or more points.

8. A system for monitoring an electric machine, comprising:

a plurality of sensors operable to measure a magnetic field associated with the electric machine at a plurality of respective points external to the electric machine; and

a control unit operable to;

receive the plurality of measurements from the plurality of sensors,

determine a combined value of the magnetic field based at least in part on the plurality of measurements,

compare the combined value to one or more expected values of the magnetic field, and

determine, based at least in part on the comparison, whether a fault is present in the electric machine.

9. The system of claim 8, wherein the control unit comprises at least one memory operable to store the one or more expected values of the magnetic field.

10. The system of claim 8, wherein the control unit is further operable to determine the combined value of the magnetic field based at least in part on an integration of the plurality of measurements.

11. The system of claim 8, wherein the control unit is operable to compare the combined value of the magnetic field to one or more expected values by comparing the combined value of the magnetic field to one or more ranges of expected values.

12. The system of claim 8, wherein the control unit determines that a fault is present in the electric machine, and

wherein the control unit is further operable to identify a fault type associated with the fault based at least in part on comparing the combined value of the magnetic field to one or more corresponding expected values associated with the fault type.

13. The system of claim 8, wherein the plurality of sensors are operable to measure the magnetic field associated with the electric machine while the electric machine is online.

14. The system of claim 8, wherein the plurality of sensors comprise magnetometers.

15. A method for monitoring an electric machine, comprising:

determining at least one value for a magnetic field associated with the electric machine;

comparing the at least one determined value to at least one corresponding expected value; and

determining, based at least in part on the comparison, whether a fault is present in the electric machine.

16. The method of claim 15, wherein determining at least one value for a magnetic field associated with the electric machine comprises measuring a magnetic field at a plurality of points external to the electric machine.

17. The method of claim 16, wherein determining at least one value for a magnetic field further comprises:

determining a combined value of the magnetic field based at least in part on an integration of the plurality of measurements.

18. The method of claim 15, wherein comparing the at least one determined value to at least one corresponding expected value comprises comparing the at least one determined value to at least one corresponding range of expected values.

19. The method of claim 15, wherein if a fault is determined to be present, the method further comprises:

identifying a fault type associated with the fault based at least in part on comparing the at least one determined value to at least one corresponding expected value associated with the fault type.

20. The method of claim 15, wherein determining at least one value for a magnetic field associated with the electric machine comprises determining at least one value for a magnetic field while the electric machine is online.