Apparatus for aligning brushes of a dynamoelectric machine

Abstract

Apparatus is disclosed for aligning brushes of a dynamoelectric machine such as a DC generator or motor to minimize arcing of the brushes. The alignment monitor processes electrical signals from brushes of a dynamoelectric machine during tests in which various levels of buck or boost current are superimposed on a preselected level of excitation current applied to the machine, and the monitor produces output signals which, together with the levels of applied buck or boost currents, are indicative of the brushholder rigging adjustment which is required to achieve the optimum rigging position for a wide range of arc-free machine operation. Included in the brush alignment monitor are filter networks for removing noise from composite signals input to the monitor, a rectifier for changing the sign of negative signal components, and networks which amplify and integrate selected high-frequency information signals to produce output signals. Also described is an alarm system which indicates the presence of brush arcing during alignment tests by comparing the output signals with a reference signal which is either preset from prior observations of brush arcing or is automatically adjustable for changes in buck and boost currents, the latter permitting the monitor to detect directly the onset of brush arcing and thus the range of arc-free operation of the machine.