wahts the reason of a peak at 50Hz in the spectrum
wahts the reason of a peak at 50Hz in the spectrum
(OP)
hi,
can anybody help me
I measure vibration of an roller bearing with defects in different shaft speeds with a vibration sensor, i convert waveform to frequency spectrum by using FFT , and analyse the result in frequency spectrum,
but i found a peak at 50Hz, I think it can be caused by electric motor but I use a DC motor,
can a dc motor cause peak at 50 hz?
can anybody help me
I measure vibration of an roller bearing with defects in different shaft speeds with a vibration sensor, i convert waveform to frequency spectrum by using FFT , and analyse the result in frequency spectrum,
but i found a peak at 50Hz, I think it can be caused by electric motor but I use a DC motor,
can a dc motor cause peak at 50 hz?





RE: wahts the reason of a peak at 50Hz in the spectrum
You can usually tell if the 50 Hz peak is due to a real effect or ac mains interference by looking at the width of the peak. If it is very narrow compared to other peaks on the spectrum, then it is probably mains interference.
Common causes are:
1) Damaged shielding on the cable linking the accelerometer to the signal amplifier or from the signal amplifier to the data logger/analyser.
Solution: replace cables, use differential amplifiers.
2) Poor earthing of mains powered equipment
Solution: Get your electrical safety officer to test the earthing of your various pieces of equipment.
3) Ground loops
Solution: Try to earth all your equipment to the same nominal earth point.
M
--
Dr Michael F Platten
RE: wahts the reason of a peak at 50Hz in the spectrum
pj
RE: wahts the reason of a peak at 50Hz in the spectrum
However that may not help in your case since it is possible that the DC motor is driven via a mains power supply, and it is the thyristors (or whatever) in this that are radiating mains frequency.
Can you describe your instrumentation setup?
Cheers
Greg Locock
RE: wahts the reason of a peak at 50Hz in the spectrum
I use test an equipment which has bearing-shaft system, driven by a dc motor. shaft is connected to motor using a belt. and bearing is 6205 ball bearing
as I investigate the spectrum in details, the magnitude of peak values at 50 hz is greater in healthy bearing and this magnitude increases with increasing shaft speeds.(from 1000rpm-4000rpm)
another point is, lower peaks at 50hz occur in defected bearings and in some cases it can not be recognized and hide in background noise.
yes our local ac supply is 50 hz but
I think if these peaks caused by the transduser or amplifier or earthing, peaks must have approximately same magnitude in defected and healthy beaaring, but its no.
and another question is why magnitude of peaks increase with
sahft speeds
regards...
RE: wahts the reason of a peak at 50Hz in the spectrum
M
--
Dr Michael F Platten
RE: wahts the reason of a peak at 50Hz in the spectrum
RE: wahts the reason of a peak at 50Hz in the spectrum
RE: wahts the reason of a peak at 50Hz in the spectrum
RE: wahts the reason of a peak at 50Hz in the spectrum