General Electric Company

Fred H Sawada

James S Bishop

Frank M Klementowski

Sterling C Barton

Chester C Carson

Federico S Echeverria

Melvin Howenstein

Llewellyn A Blaize

High noise immunity instrumentation for monitoring brush arcing in a dynamoelectric machine is disclosed. In a preferred form the instrumentation includes a stabilized variable threshold discriminator operative in conjunction with a feedback network and a non-linear high frequency amplifier to provide a discriminator threshold which increases with increasing levels of background noise so that only the arc indicative portions of the signal are passed. A substantial increase in the signal to noise ratio is obtained. The feedback network includes a relatively long time constant integrator and buffer amplifier. Further, to provide an alarm upon the occurrence of brush arcing, an alarm network is provided which includes a comparator for continuously comparing the arc indicative signal with a reference signal which is automatically adjusted to compensate for changes in the average level of the signal from the non-linear high frequency amplifier. This compensation provides for automatically resetting the alarm comparator. This is achieved by providing a second integrator having a time constant somewhat longer than the first integrator. By appropriately selecting the relative time constants of the first and second integrators, resolution of the alarm network is narrowed to a unit time basis, thus quantifying the measurement to provide an indication of the condition of the brushes.

High sensitivity brush arcing monitor for a dynamoelectric machine

An 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; 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, respectively, a high-pass filter, a clipping network, rectification means, a second high-pass filter, a discriminator, an rf amplifier and a peak integrator with alignment indicating means. Also included is an rf generator network which is used to test the operation of the alignment apparatus.

Brush alignment apparatus

An electronic control system to automatically determine the validity of an apparent overheating signal from an overheat monitor of a gas-cooled dynamoelectric machine and reduce machine load or indicate a monitor malfunction. Upon receipt of an apparent overheat signal by the control system, filtration of the monitored cooling gas is automatically initiated to remove pyrolysates released into the gas by overheated elements within the machine. A normal monitor response is thereby effected, provided the overheat signal is valid. If filtration of the monitored cooling gas fails to elicit a normal response within a preselected time period a monitor malfunction is indicated. The control system initiates a scheduled reduction in machine load either subsequent to validation of overheating or as verification is initiated, and if a valid indication of overloading persists, trips the excitation and remaining load from the machine. Redundant current paths, high-speed solid-state comparators, and timing elements are included in the control system for verifying the monitor signals.

Automatic control for processing signals from an overheat monitor of a

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.

Apparatus for aligning brushes of a dynamoelectric machine

Apparatus is described for monitoring arcing of brushes used in the transfer of current signals to and from the field of a generator. Electrical signals from the brushes, which are applied to the disclosed monitor for analysis, may include brush arcing signals to be monitored and in addition high-amplitude noise spikes in the same frequency band as the brush arcing signals, the noise spikes thus masking accurate detection of low level brush arcing by conventional devices. A two-stage clipping network is provided in the monitor to raise the brush arcing/noise ratio and thus mitigate the masking effect of the noise spikes without loss of a portion of sampling interval during which arcing may occur. Other features described as part of the brush monitor are discriminator diodes biased for constant threshold sensitivity to maintain arc detection accuracy over a wide range of ambient temperatures; an alarm system which functions to indicate and record the occurrence of brush arcing so that corrective action may be initiated to prevent serious damage to rotor slip rings and brush components; and a reference signal generator which automatically adjusts the level of reference signal used in the alarm system for changes in generator noise level.

Apparatus for monitoring arcing of brushes in a dynamoelectric machine

A system is provided for monitoring a composite signal at the brushes of a generator. The composite signal includes an information signal representative of brush arcing and a recurring noise signal. The system includes a gating network which eliminates the noise signal and passes the information signal therethrough. Timing of the gating network is controlled by a pulse forming network. On the occurrence of a noise signal the pulse forming network produces a disabling signal of predetermined time period exceeding the duration of the noise signal. The gating network blocks all signal passage therethrough for the duration of the disabling signal and thereafter passes signals until the occurrence of the next noise signal. Means is also provided for indicating when the information signal exceeds a predetermined magnitude.

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Scotia, NY, United States of America

Fred H Sawada