mech or elec vibration?

[thewaterman]

Hello,
Hope you can help! our contractor has recently installed 110 off new motors on our water treatment plant aeration lanes, they are 15kw on outside lanes and 11kw further along, they are drving a spash paddle through a gearbox, i think they are weg motors, flender box's, our vibration worker was checking them today and was having kittens over what he was finding, He said they are all over the place and not consistent, The motors (switchable on/off) and driven through a single vsd for two motors, pfc is installed but i have not seen a harmonic filter. we have disconnected the drive and found that there is still some resonannce in the motor but not as severe as when coupled, could it be harmonics? i have inspected the electricals on the mcc and found consistantly in one area off the mcc a wire that seems to be hotter the the others across the phases, it's around 72 degrees others are 30degrees. some are causing real ground shudder around the motor, They will break up before long!!! good job we have not signed the off yet..any help please..
joe

 

[electricpete]

What specifically caused your vibration guys to have kittens?
;-)

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[electricpete]

I should clarify, it's a joke but also a question. What did the vib guy see (what frequencies?)

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[electricpete]

What is ground shudder?

Do you think a hot spot is causing motor vibrations? I guess it could cause unbalanced voltage and 2*LF, but wouldn't think the magnitude would be very high.

Regardless of the relationship to vibration, 72C rise on one phase with 30C rise on the others deserves to be investigated/corrected on its own regardless of relationship to vibration.

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[edison123]

thewaterman

Very vague post. I suggest you delete it (you can Red Flag your own post and ask the mods to delete it) and then repost it with the vibration data along with other observations. "They were all over the place" doesn't cut it.

Muthu

http://www.edison.co.in

 

[thewaterman]

not sure on exatct vib readings until i see him again tommorow. The virbration guy said the vibration frequencies were not consistant with each other, and not one set patteren was observed, the vibrations are variable depending in the speed you run the motors, at certain speeds you don't need a vibration tool to tell there is somthing wrong, motors spaced are about 15-20ft apart on a concrete plint that is about7ft wide water runs along the lanes, the cable runs to the mcc are at longest lenth about 80 meteres, i will let you know what they do with the hot wires i use a FlirT360 for the inspection's.
Thanks for your help.

 

[thewaterman]

the vibration resonnance was 12 m/s at 1100rpm, what was also found that when motor was uncoupled from the drive it was showing 7 m/s at 1100rpm. 1100 seems to give the most vibration. having two motors going through 1 vsd is not common on our works.