Well, first of all you can spell frequency correctly. Second, you can word your question in a way that is comprehensible - and with enough detail - to allow people to give you some guidance.
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Thank you Drej. Frequency. There are 6 motors and their revolution speed is 3000RPM. I want to calculate frequency of the system. OIf there are only one motor, I can calculate of frequency of the system as 50Hz. How can I calculate the frequency produced by 6 motors?
femboy,
Perhaps you could post a picture, or some more information about the geometry that you're analyzing? The number of motors and their operating speed should not matter to your FE modal analysis, other than adding weight (and perhaps stiffness) to your assembly.
You'll want to compare the natural frequencies that you compute to the forcing frequencies that are generated by the motors, and perhaps the 2/rev, 3/rev, 4/rev frequencies (and so on) when post-processing. If you're dealing with a geared drive, pay special attention the number of gear teeth and the rotating speeds of the gears: these are possible sources of vibration forcing.
A good tool for finding potential harmonic problems is a Campbell diagram. If the operating speed of the motors is near a crossing on a Campbell diagram (especially at the lower per-rev lines), you may have harmonic excitation problems.
//signed//
Christopher K. Hubley
Mechanical Engineer
Sunpower Incorporated
Athens, Ohio
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