I need some help from someone who is more of an electrical guru than me. Attached is a Peakvue spectrum that shows 2XLF with harmonics. Oridinarily not a big deal. But what I am seeing are sidebands equal to 1/2 order + Slip frequency around 240, 360, and 720 Hz. There are also TS sidebands around 120 Hz. Also a 1XTS peak is present. Amplitudes are not really that high (1.26Pk in waveform) so I am only going to trend this for now. This is taken with a 1000Hz HP filter so evertying that is seen is happening in the higher frequency ranges.

elect.freq.doc (27 Kb, 40 downloads)

Is this a vibrating screen? AC Induction motor started across the line? What is the operating frequency of the screen? Is this a sudden onset or gradual increase?

This is a centifugal screen. AC induction motor no softstart. 6.08 Hz operating frequency of the screen. This equipment has been out of operation for a couple of years. It was just now reincorpurated into the system again. This is a vertically mounted motor. Could there possibly be some loose coils or something of that nature? It may just be coincidence, but I find it odd that the sidebands match up with 1/2 order plus slip frequency. I can't find any thing written about that particular frequency calculation.

Scott,

Did you collect high resolution readings? Are you completely sure that the frequencies are 120 hz and harmonics. I'm thinking it could also be a bearing frequency.

Also what high pass filter setting is being used with the peakvue measurement?