Direct current machine monitoring system and method

1. A direct current machine monitoring system comprising:

(a) a sensor configured to monitor a load current of the machine and provide a signal indicative of an alternating current component of the load current; and

(b) a computer configured for

(i) transforming the load current to provide a time domain transformation of the alternating current component of the load current,

(ii) identifying features in the time domain transformation corresponding to sparking, and

(iii) assessing a condition of the direct current machine using the features.

2. The direct current machine monitoring system of claim 1 , wherein the computer is further configured for:

determining a sparking frequency of the direct current machine using the features;

determining a sparking intensity of the direct current machine using the features; and

wherein the assessing is performed using the sparking frequency and the sparking intensity.

3. The system of claim 2 , wherein the determining the sparking intensity includes:

determining a magnitude of a feature in the time domain transformation.

4. The system of claim 2 , wherein the determining the sparking frequency includes:

determining a frequency of occurrence of a feature in the time domain transformation.

5. The system of claim 2 , wherein the assessing includes:

determining a sparking index based on the sparking frequency and the sparking intensity.

6. The system of claim 5 , wherein the assessing further includes:

comparing the sparking index to a threshold value.

7. The system of claim 5 , wherein the assessing further includes:

performing statistical analysis using the sparking index.

8. The system of claim 5 , wherein the determining the sparking index includes at least one of:

multiplying the sparking frequency and sparking intensity; and dividing a sum of a plurality of sparking intensities by the sparking frequency.

9. The system of claim 1 , wherein the transforming is performed using a wavelet transform.

10. A direct current machine monitoring system comprising:

(a) a sensor configured to monitor a load current of the machine and provide a signal indicative of an alternating current component of the load current; and

(b) a computer configured for

(i) transforming the signal using a wavelet transform to provide a time domain transformation of the signal,

(ii) determining a magnitude of at least one feature in the time domain transformation of the signal to provide a sparking intensity,

(iii) determining a frequency of occurrence of the at least one feature in the time domain transformation to provide a sparking frequency, and

(v) assessing a condition of the direct current machine using the sparking intensity and the sparking frequency.

11. The system of claim 9 , wherein the assessing includes:

determining a sparking index based on the sparking frequency and the sparking intensity.

12. The system of claim 11 , wherein the assessing further includes:

comparing the sparking index to a threshold value.

13. The system of claim 11 , wherein the assessing further includes:

performing statistical analysis using the sparking index.

14. A method of monitoring a direct current machine, the method comprising:

sensing a load current to the direct current machine to provide a signal indicative of an alternating current component of the load current;

transforming the signal to provide a time domain transformation of the alternating current component of the load current;

identifying features in the time domain transformation corresponding to sparking; and

assessing a condition of the direct current machine using the features.

15. The method of claim 14 , further comprising:

determining a sparking frequency of the direct current machine using the features,

determining a sparking intensity of the direct current machine using the features, and

wherein the assessing is performed using the sparking frequency and the sparking intensity.

16. The method of claim 15 , wherein the determining the sparking intensity includes:

determining a magnitude of a feature in the time domain transformation.

17. The method of claim 15 , wherein the determining the sparking frequency includes:

determining a frequency of occurrence of a feature in the time domain transformation.

18. The method of claim 15 , wherein the assessing includes:

determining a sparking index based on the sparking frequency and the sparking intensity.

19. The method of claim 18 , wherein the assessing further includes:

comparing the sparking index to a threshold value.

20. The method of claim 18 , wherein the assessing further includes:

performing statistical analysis using the sparking index.

21. The method of claim 14 , wherein the transforming is performed using a wavelet transform.

22. A method of monitoring a direct current machine, the method comprising:

sensing a load current to the direct current machine to provide a signal indicative of an alternating current component of the sensed current;

transforming the signal using a wavelet transform to provide a time domain transformation of the alternating current component of the sensed current;

determining a magnitude of at least one feature in the time domain transformation to provide a sparking intensity,

determining a frequency of occurrence of the at least one feature in the time domain transformation to provide a sparking frequency, and

assessing a condition of the direct current machine using the sparking intensity and the sparking frequency.

23. The system of claim 22 , wherein the assessing includes:

assigning a sparking index based on the sparking frequency and the sparking intensity.

24. The system of claim 23 , wherein the assessing further includes:

comparing the sparking index to a limit value.

25. The system of claim 23 , wherein the assessing further includes:

performing statistical analysis using the sparking index.