High sensitivity brush arcing monitor for a dynamoelectric machine
First Claim
1. In apparatus for monitoring arcing of brushes in an electrical generator, such apparatus being of the type including means receiving from at least one brush a composite signal comprised of high frequency brush arcing components, low frequency components, noise spikes, and high frequency background noise whose amplitude depends upon generator loading;
- signal conditioning means removing said low frequency components and attenuating said noise spikes to a preselected amplitude to provide a conditioned signal;
a discriminator network having a signal threshold limiting said conditioned signal to signal components of one polarity above said threshold;
an amplifier producing an amplified signal from the conditioned signal from said discriminator; and
a first integrator integrating said amplified signal to produce a first integrated signal indicative of brush arcing;
an improvement comprising;
a feedback network including an auxiliary integrator for integrating said amplified signal to provide a feedback bias signal indicative of the background noise contained in said amplified signal, and a buffer amplifier for applying said feedback bias signal to said discriminator, said discriminator being responsive to said feedback bias signal to vary said threshold level up or down as a function of said signal.
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Accused Products
Abstract
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.
26 Citations
10 Claims
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1. In apparatus for monitoring arcing of brushes in an electrical generator, such apparatus being of the type including means receiving from at least one brush a composite signal comprised of high frequency brush arcing components, low frequency components, noise spikes, and high frequency background noise whose amplitude depends upon generator loading;
- signal conditioning means removing said low frequency components and attenuating said noise spikes to a preselected amplitude to provide a conditioned signal;
a discriminator network having a signal threshold limiting said conditioned signal to signal components of one polarity above said threshold;
an amplifier producing an amplified signal from the conditioned signal from said discriminator; and
a first integrator integrating said amplified signal to produce a first integrated signal indicative of brush arcing;
an improvement comprising;a feedback network including an auxiliary integrator for integrating said amplified signal to provide a feedback bias signal indicative of the background noise contained in said amplified signal, and a buffer amplifier for applying said feedback bias signal to said discriminator, said discriminator being responsive to said feedback bias signal to vary said threshold level up or down as a function of said signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
- signal conditioning means removing said low frequency components and attenuating said noise spikes to a preselected amplitude to provide a conditioned signal;
Specification