Airborne Noise Testing

[eaglet]

Does anyone no where I can find a good listing of causes for spikes I see at different frequencies of airborne noise testing of AC motors. I know that certain problems manifest themselves at various frequencies, such as fan problems, electrical noise, bearing problems,..etc., but I have been unable to find a complete listing.

Thanks

 

[GusD]

Hi eaglet

If I understand your question correctly as being related to the generated vibration/noise frequencies of different
rotating machinery,all of the frequencies except the Electrical noise ,they will be related to the Fundamental speed.As the speed changes so do the calculated frequencies.Your Electrical noise will be directly related to the Line Frequency (2xLF) (Eg 120Hz/7200cpm) on 60hz Power.All others, such as Bearing Defect Frequencies will be directly related to the speed.The # of blades in a Fan x the RPM will give you what is commonlly called Blade Pass Freq.There are Formulas to calculate your Bearing Freq,for any given speed.Some Vibration software calculates these values automaticaly once the RPM is inputed.
Speed is the Key.Gearmesh in a gearbox will be a factor of the # of teeth x the input speed.As the speed varies so do the frequency of defects.

GusD

 

[jbartos]

Suggestion: Visit

http://www.reliance.com/mtr/pcnomn.htm

etc. for more info