On Tuesday 04 August 2020 15:05:10 Thaddeus Waldner wrote: > Can you or someone else please expand on that? > > Most VFD that I am familiar with operate between 10khz and 20khz. I > personally like to configure them upwards of 16khz because I find the > squealing noise annoying. I suppose that the main reason to not do > that is that it increases switching losses. > > Do any servos or VFD systems actually run their base frequency higher > than 20khz? > Most try to stay above 17 or 18 khz. The ferrite in the transformers is megneto-strictive, which is usually where the noise comes from.
> If not, where do those harmonics come from? square waves have no theoretical limit to the harmonics generated, so the limit is usually the design choice of how fast the transistor can switch, and higher speed costs money, more often than not its how fast the lower level driver can charge or discharge the gate capacitance of the power fet doing the actual switching. The longer it takes to do the switch translates into a higher time for the switching transistor to be in ohmic territory, increasing its heating. The driver transistor might need to src or sink 20 amps or more during this edge transition. For perhaps 5 ns? > > On Aug 4, 2020, at 11:51 AM, Jon Elson <el...@pico-systems.com> > > wrote: > > > > On 08/04/2020 08:00 AM, Matthew Herd wrote: > >> I am guessing that the source of the trouble is probably the VFD, > >> as 80kHz seems like a plausible base frequency for driving an AC > >> motor. Only the USC should be operating at a frequency higher than > >> 60Hz other than the VFD. The machine uses three gecko drives and > >> large steppers, so it’s not very sophisticated. > > > > I think 80 KHz is a multiple of the frequency of the Gecko drives. > > You might try turning off the power to them and see if the issue > > changes. > > > > > > Jon > > > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
