Automated apparatus for long-term testing of electrical brushes

The meaningful evaluation of electrical brushes and the development of novel electrical sliding contacts can require exhaustive testing. An automated testing system has been developed in which a personal computer both controls test parameters for a matched brush pair running on the same rotor according to a preselected program, and stores test data. Specifically controlled are the brush forces, brush polarity, and the current. The voltage drops across each of the two brushes, their wear, and the rotor temperature are monitored. Additionally, traverses, meaning brief periods of ramping the current up and down between preselected limits while measuring the associated voltage drops, can be programmed into the tests. The duration of the various phases in complex testing programs and the intervals between data taking can be varied between seconds and months, but the system is switched off automatically when the voltage across either of the two brushes or the rotor temperature exceeds a preselected value. The accumulated data can be recalled in various graphical representations and program changes can be made at any time without interrupting the test