Digital filtering of EL CID data
First Claim
1. An electrical generator inspection system for detecting insulation breakdown between two or more adjacent laminates of a generator stator, and operable to provide enhanced digital signals while maintaining signal integrity, comprising:
- an electro-magnetic core imperfection detector for providing an analog signal representative of fault currents detected due to defects in the insulation between laminates along the stator core, said analog signal comprising the amplitude of the fault current versus the distance traversed along the length of the stator core;
an analog-to-digital convertor coupled to said detector for converting the analog signal to a digital signal; and
a low-pass digital elliptic filter of at least the third order coupled to said converter to substantially remove noise from said digital signal while simultaneously maintaining signal integrity.
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Accused Products
Abstract
An electrical generator inspection system comprises an electro-magnetic core imperfection detector that provides an analog signal representative of fault currents detected between adjacent laminations of a stator core; an analog-to-digital converter coupled to the detector for converting the analog signal to a digital signal; a digital filter coupled to the output of the converter for digitally filtering the digital signal to remove noise therefrom; and means for storing predetermined signal criteria and for comparing the filtered digital signal to the predetermined criteria to determine the location of the insulation defects along the stator core. In one embodiment, the system further comprises means for storing the filtered digital signal in a memory.
32 Citations
8 Claims
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1. An electrical generator inspection system for detecting insulation breakdown between two or more adjacent laminates of a generator stator, and operable to provide enhanced digital signals while maintaining signal integrity, comprising:
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an electro-magnetic core imperfection detector for providing an analog signal representative of fault currents detected due to defects in the insulation between laminates along the stator core, said analog signal comprising the amplitude of the fault current versus the distance traversed along the length of the stator core; an analog-to-digital convertor coupled to said detector for converting the analog signal to a digital signal; and a low-pass digital elliptic filter of at least the third order coupled to said converter to substantially remove noise from said digital signal while simultaneously maintaining signal integrity. - View Dependent Claims (2, 3)
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4. In an electrical generator inspection system employing an electro-magnetic core imperfection detector which provides an analog signal representative of fault currents detected due to defects in the insulation between laminates along the stator core, a method comprising the steps of:
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converting the analog signal provided by said detector to a digital signal; digitally filtering said digital signal using at least a third order low-pass digital elliptic filter to substantially remove noise from said digital signal without destroying the integrity of the digital signal; storing predetermined signal criteria in a computer means; and comparing said filtered digital signal to said predetermined signal criteria to automatically determine the location of said insulation defects along the stator core. - View Dependent Claims (5)
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6. An inspection system to detect insulation breakdown in the stator core of an electrical generator and operable to provide enhanced signals while maintaining signal integrity, said system comprising,
a plurality of sensors mounted on a carriage adapted for movement along said stator core, said carriage being electrically connected to an electro-magnetic core imperfection detector to thereby provide an analog signal representative of fault currents due to defects in the lamination of said stator core; - said analog signal comprising a magnitude of the fault current versus the distance traversed along the stator core;
an analog-to-digital convertor coupled to said electro-magnetic core imperfection detector for converting said analog signal into a digital signal; and a digital filter coupled to said analog-to-digital converter to remove noise from said digital signal, without destroying the integrity of the digital signal, said digital filter being in the form of the following expression;
##EQU3## wherein X(z) comprises the un-filtered digital signal from the analog-to-digital convertor, a(n) and b(n) are filter coefficients, and Y(z) is the resultant filtered output. - View Dependent Claims (7, 8)
- said analog signal comprising a magnitude of the fault current versus the distance traversed along the stator core;
Specification