Patent ID: 8120503

Claim:
A worn brush monitoring system for monitoring a plurality of brushes of an electrical machine comprising: a plurality of mounted flags configured to be in moveable communication relative to a wear of each of the plurality of brushes; and an electrical recording circuit including: at least one impedance device configured to provide impedance data; a recording device configured to detect changes in electrical characteristics in the electrical recording circuit resulting from changes in a switch state, the switch state defined by the interaction between the mounted flags and the electrical recording circuit, as a result of brush wear; and at least one switch having a contact plate interactable with at least two of the plurality of mounted flags at different points along a length of the contact plate and an impedance dependent on the length of the contact plate, wherein an interaction with the contact plate at the different points causes the contact plate to impart different impedances to the impedance device, wherein the recording device uses a difference between the different impedances to identify at least one of the plurality of brushes as being worn.