Daniel George Roth

US Patent:

7990668, Aug 2, 2011

Filed:

May 22, 2008

Appl. No.:

12/154328

Inventors:

Timothy Robert Day - Racine WI, US
Daniel Patrick Roth - Pewaukee WI, US

Assignee:

Cooper Technologies Company - Houston TX

International Classification:

H02H 3/00
H02H 7/00

US Classification:

361 65, 361 79

Abstract:

Device protection using temperature compensation. A logic module associated with groups of capacitors adjusts complex impedance planes associated with the capacitor groups to account for ambient temperature variations. In particular, the logic module is configured to adjust a center of a circle of each complex impedance plane based on an average impedance. The average impedance for a selected capacitor group includes impedance measurements for groups other than the selected group, to prevent capacitor failures in that group from skewing the average. The logic module can adjust the circle center in response to changes in average impedance over periods of time. For example, the logic module can filter measured differences in average impedance using a low pass filter, to distinguish slow impedance changes caused by temperature variations and rapid impedance changes caused by capacitor failures. The logic module can adjust the circle center in accordance with the filtered difference value.