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#1
Start by
Daryl Keys C.E.T.
09-23-2013 10:24 AM

Carrier frequency of AC motor

Does anyone know where to find documentation describing the effect of the carrier frequency of an AC on motor vibration and audible noise?
09-23-2013 01:12 PM
Top #2
Seok Joo Jang
09-23-2013 01:12 PM
There are a lot of technical documentations about audible noise caused by the carrier frequency. But I haven't read documentation about motor vibration. As for the vibration, what frequency range are you interested in?
09-23-2013 05:41 PM
Top #3
Ken Schmanski
09-23-2013 05:41 PM
You can find a lot of info on the effect of switching frequency on audible noise. The sound you hear is twice the frequency of the switching frequency. At 5K, the audible frequency would be 10K. The higher the switching frequency, the more load on the VFD output devices. Reason why larger drives are derated or limited at higher switching frequencies. The lower the frequency, the more annoying the motor audible noice will be.
09-23-2013 08:31 PM
Top #4
Daryl Keys C.E.T.
09-23-2013 08:31 PM
The carrier frequency range would be between 1.5kHZ and 3KHZ
09-23-2013 10:48 PM
Top #5
Daryl Keys C.E.T.
09-23-2013 10:48 PM
Thanks, I’ll contact them
09-24-2013 01:35 AM
Top #6
Dean Boe
09-24-2013 01:35 AM
I would like to add to Mr. Schmanski's comment. Carrier frequency in fact causes the audible noise. You can diminish the noise with high frequency ripple filters which will add cost to the installation. This may be necessary in places where the public or employees are in close proximity to the SMPS or VFD. In most cases of a VFD you may increase the carrier frequency beyond the audible level of human hearing level, however, not without drawback. The drawback is simply that the VFD now has higher losses in the Power Stack due to higher switching frequencies and may have the need to be de-rated in terms of highest continuous current available.
09-24-2013 03:57 AM
Top #7
Daryl Keys C.E.T.
09-24-2013 03:57 AM
It is the reaction that the motor frame and windings have to carrier
frequency that I’m interested in. Not looking for solutions just
documentation.
09-24-2013 06:25 AM
Top #8
- -.
09-24-2013 06:25 AM
Carrier Frequency along with Lead Length will have impact on the windings as will Common Mode have an impact on the bearings.
Visit our web page http://www.transcoil.com/Support/Documentlibrary.htm
Carrier_Suppression_In_Pumps is a very good paper to read.
Contact me for more information if desired.
09-24-2013 11:11 AM
Top #9
Eddie Mayfield
09-24-2013 11:11 AM
Daryl, your initial question was on the effect of carrier on the motor, not the VFD I think.. as others on here have stated, the relationship between audible noise and carrier frequency is fairly straight forward.. lower freq = higher noise.. but as a practical matter. most inverters come set up for freqs out of the audible range, so its usually not an issue. There are other problems, indirectly related to carrier frequency, but are commonly only problematic with coupled with long cable lengths.. that can cause severe problems with motors.. due to reflective waves.. Rockwell has a good paper on this (as do many others) http://abweb.rockwellautomation.com/support/abdrives/documentation/techpapers/ieee/pcic. . Hope this helps.. Eddie
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