James,

Can you expand the 1x to see the distance between the sidebands

Might be a rotor problem in the motor.

See the attached picture of your spectrum.

Thanks and Have a Great Day

Ralph.

Hi Ralph

So from what I can make out they don't seem like sidebands but they are around 1.8-2.2 CPM apart. Would that reduce the possibility of it being a rotor bar issue ?

Like you mentioned I would have expected to see around 60cpm sidebands for rotorbar issues. 15 slip x 4 poles.

I'm curious as to why I would see such a dramatic difference between the NDE and DE, especially given the layout.

Also why would I have a fairly normal phase at the non drive end between the vertical and horizontal. But then almost in phase on the drive end side ? Just seems rather bizarre.

Un not sure those are sidebands, is the speed of the motor constant?

@Registered Member posted:

Un not sure those are sidebands, is the speed of the motor constant?

Yeah they don't look like sidebands either. The speed is fixed yes, not sure what else to try to determine what's happening. got to wait a while until I can use the MA camera on it but this may be a few months down the line...

@Registered Member posted:

Hi Ralph

So from what I can make out they don't seem like sidebands but they are around 1.8-2.2 CPM apart. Would that reduce the possibility of it being a rotor bar issue ?

Like you mentioned I would have expected to see around 60cpm sidebands for rotorbar issues. 15 slip x 4 poles.

I'm curious as to why I would see such a dramatic difference between the NDE and DE, especially given the layout.

Also why would I have a fairly normal phase at the non drive end between the vertical and horizontal. But then almost in phase on the drive end side ? Just seems rather bizarre.

James,

Thanks for the reply.

In your waveform, what are the frequency spacing between "the colored modulation peaks"?

Ralph

Hi Ralph

I've attached a file to try and get the frequencies, sorry if its not quite as you want it, this is still a fairly new system for me.   

Hello James,

Concerning the waveform questions I had, it is sometimes difficult to put things in understandable words, well. at the least, for me.

Your spectrum appears to need more resolution to separated the sidebands and determine their origin. A 100 Hz Fmax and 6400 or 12,800 line should help. I am basing this on the "wide" empty area to the left of the "marked" 1x peak.

In my attached picture of your waveform plot, can you determine the frequency separation of the "black dot peaks" marked and then find these in the high resolution spectrum? These black dot peaks appear to be modulated themselves by what may be the 4 pole passage of the rotor.

What version of CSI software do you have?

Thanks and Have a Blessed Day,

Ralph

Hi Guys, so I went to take a reading today but unfortunately it wasn't running. What I was able to do is get them to run it very briefly so I could take a coast down reading... I've attached the coast down spectrum, it looks like the Coast down shows a range starting from 937cpm to around 1875cpm. This would encompass my 1485 running speed.

The weight of the motor is 1491KG, Can anyone tell me how I would work out how much weight to add to get it away from this range?

@Registered Member posted:

Hi Guys, so I went to take a reading today but unfortunately it wasn't running. What I was able to do is get them to run it very briefly so I could take a coast down reading... I've attached the coast down spectrum, it looks like the Coast down shows a range starting from 937cpm to around 1875cpm. This would encompass my 1485 running speed.

The weight of the motor is 1491KG, Can anyone tell me how I would work out how much weight to add to get it away from this range?

James,

Impressive spectrum.

But comparing this spectrum to the regular route spectrum, to me, it (the 1,312 cpm amplitude) is not showing under normal running conditions, but that may be (not showing) because the coastdown plot posted doesn't include this frequency (1,311).?????.

This 1,311 cpm peak may be far enough away from the 1485 cpm running speed and only happens on startup and shutdown. as the system goes through a natural frequency and that it (1,311 cpm) does not show in normal running mode.

I would still like to see a spectrum of 200 Hz Fmax and 6400 or 12,800 lines, if possible, so as to separate all the possible sidebands in normal running mode. Unless, it is running close to another natural frequency closer to 1x.

The "wide" noise band next to the left of 1x in your route data may be the part culprit

Just my opinion and I could be totally wrong.

Have a Great Day,

BTW: do you have the waveform belonging to the coastdown spectrum? Have you tried a bump test with the system down to see how "long" the ring-down is from the 1311 cpm frequency?

Ralph

no you might be totally right it does seem rather odd ! The picture above is the spectrum taken at 1560cpm with 12800 lines ive had to zoom in a little to get a better image. the distance between the sideband is 0.36cpm so a very small difference there!

this is the autocorrelated time waveform for the hi res spectrum above, not seen a waveform like this to be honest, it looks like some form of beating/modulation?

this is the full waveform when zoomed out

and finally here is the autocorrelated circular format for anyone who may be able to interpret this

@Registered Member posted:

no you might be totally right it does seem rather odd ! The picture above is the spectrum taken at 1560cpm with 12800 lines ive had to zoom in a little to get a better image. the distance between the sideband is 0.36cpm so a very small difference there!

Thanks James,

One more question.

See the attached doc file questions.

Ralph

@Registered Member posted:

no you might be totally right it does seem rather odd ! The picture above is the spectrum taken at 1560cpm with 12800 lines ive had to zoom in a little to get a better image. the distance between the sideband is 0.36cpm so a very small difference there!

Thanks James. This is sort of strange for there to be sidebands off the 1x at such a CLOSE distance........

What is the motor driving, a gearbox? and what is the final rpm of the driven part?     If agitator, what is its rpm snd how many blades or paddles?

Ralph

Why use peak hold averages spectrums if you can make waterfall plots, in my opinion 1000hz 400 lines will give you a very fast spectrum and any other harmonics will rise at a resonance "zone" which will give you a better confirmation of resonance

Agree with Ralph, phase at feet and what's this motor driving, motor - gearbox - rollers for a pellet press, how is the feeding "controlled" more material will slow down the motor (increased load) once the motor is free it will spin a little faster, this might look like a weird sidebands when using a averages or a long acquisition time.

Circular waveform of the high resolution spectrum is now always the best choice, try with 10khz and 1600 lines.

It's just my opinion and I could be totally wrong

a couple of motion amplification videos to show the movement of the base. which is allowing the motor to move a lot more than what is acceptable