On Fri, 15 Dec 2006, Jon Elson wrote: > Date: Fri, 15 Dec 2006 14:08:46 -0600 > From: Jon Elson <[EMAIL PROTECTED]> > Reply-To: "Enhanced Machine Controller (EMC)" > <[email protected]> > To: "Enhanced Machine Controller (EMC)" <[email protected]> > Subject: Re: [Emc-users] Mesa m5i20 PWM frequency ? > > Peter C. Wallace wrote: > >> 50 KHz is pretty high for PWM, as the switching losses in the HBridge go up, >> and the dead time becomes more of the total cycle time. >> > My first cut at a PWM servo drive ran at 100 KHz, using analog components to > make a velocity servo amp with the traditonal ramp generator/comparator > to produce the PWM pulses. > > At 50 KHz, the switching losses are small compared to the conduction > losses at > 20 A continuous output current. This is helped greatly by using the > sign/magnitude > modulation scheme instead of synchronous antiphase modulation. The > switching > losses at 0% PWM are zero!
But whats the dead time? If you are not using a closed loop current control, (that is the controller PWM runs the HBridge directly) the dead time will become a significant part of your 50 KHz cycle time leading to non-linearity in PWM versus motor voltage. At least that my experience, high PWM results in higher losses with no particular advantages (unless you are running a motor with inductive/mechanical time constants so fast that it matters -- perhaps a voice coil) > > Jon > > > ------------------------------------------------------------------------- > Take Surveys. Earn Cash. Influence the Future of IT > Join SourceForge.net's Techsay panel and you'll get the chance to share your > opinions on IT & business topics through brief surveys - and earn cash > http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
