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REDUCTION OF ACOUSTICAL NOISE EMISSION IN AC-MACHINES BY INTELLIGENT DISTRIBUTED RANDOM MODULATION
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| Author(s) |
John K. Pedersen; Frede Blaabjerg; Per S. Frederiksen |
| Abstract |
AC-machines driven by PWM-VSI inverters emit acoustical noise. The dominating frequencies in the acoustical noise emission spectra are placed around the switching frequency of the inverter and multiples of this. To reduce the emitted noise a quasi random modulation strategy is proposed. Quasi random modulation means that the switching frequency is varied within a prespecified frequency band. The modulation gives the emitted noise a more "acceptable" sound for the human ear due to the distinct tones are less significant. The modulation strategy is improved in order to distribute the output voltage spectra more uniform. Measurements show an almost uniform distribution of the voltage spectra when a special weight function of the distribution of the random modulation frequency is used. Further improvements can be done by considering the mechanical resonance frequencies of the AC-machine. Test on a pump system shows that omitting the switching frequencies around estimated mechanical resonance frequencies of the AC-machine and Ioad reduces the emitted acoustical noise significantly. It is concluded that an almost silent AC-machine is obtained even at low switching frequencies. |
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| Filename: | Unnamed file |
| Filesize: | 3.547 MB |
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| Type |
Members Only |
| Date |
Last modified 2019-05-23 by System |
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