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   -> Volume 9, Issue 5

Question: Wavelets and Fault Diagnostics
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"Mr. Al Kazzaz Saad Ahamed" (

PostPosted: Mon Jun 12, 2000 6:55 am    
Subject: Question: Wavelets and Fault Diagnostics
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#26 Question: Wavelets and Fault Diagnostics

Dear Sir,

Kindly accept my regards and congratulation for your
commendable work on wavelet. Your work inspires freshers like me to
devote attention on this field.

Sir, may I would be greatful if can clarify some doubt about
the application of wavelet in the area of fault diagnostic of
electrical machine.

My knowledge about wavelet is limited and I am trying to
explore the feasibility of using wavelet algorithm to state the health
of electrical machine via vibration signal. As a primary
investigation, I applied wavelet algorithm (using daubechiese6) to a
variable frequency sinusoidal signal (10-1500 Hz) sampled at 4kHz and
with 20000-sample length. Then I calculated the FFT of each decomposed
data but the results is not coming as I expected. After each
decomposition the number of sample become half and the sampling
frequency also become half and the step frequency between the spectrum
harmonics must be same. So that, I except that the spectrum after
first decomposition contain only the peaks of 500 to 1000 Hz and the
second contain only the peaks of 250 to 500 Hz and so on. Also,
alising problem was appear after the reduction the of sample by two,
because the sampling frequency become half. Is this right? In
addition, I faced a problem in referring the amplitude of the
decomposed signal with the original one. I hope you will kindly
comply with the request.

With regards

Yours faithfully,

Sa'ad Ahmed Al kazzaz
R/S Elect. Eng. Dept.
University of Roorkee
Roorkee 247667, India
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