On Fri, 12 Nov 2010, Andy Pugh wrote: > Date: Fri, 12 Nov 2010 17:34:50 +0000 > From: Andy Pugh <a...@andypugh.fsnet.co.uk> > Reply-To: EMC developers <emc-developers@lists.sourceforge.net> > To: EMC developers <emc-developers@lists.sourceforge.net> > Subject: Re: [Emc-developers] BLDC Driver > > On 12 November 2010 17:12, Mario. <emef...@gmail.com> wrote: > >> And as for "flat-topped sine wave, are you sure it is NOT a space vector >> wave? When I did SVPWM on PIC18F452 some 6 years ago, it made a lovely sine >> wave measured from phase to phase, > > Surely what you are describing there is more related to the drive then > to the motor though? > > Anyway, none of this matters to my HAL component, the inputs, outputs > and modes are exactly the same regardless of subtle motor or drive > differences. >
The "flat topped sine wave" is measured EMF when a motor is spun. My point was that the wave shape differences in most PMSMs (Permanet Magnet Synchronous motors) are small, and sine wave drive will work well for most. Space vector has more torque ripple (they are "ticky" at low speed) but allows higher speeds. A fancy drive system might switch from sinusoidal drive to space vector above a set RPM. SR motors are another thing entirely, they are cheaper for large sizes since no permanent magnet is required and also very rugged (can't demagnetize). The disadvantage is they have is more complicated drive circuitry and higher torque ripple. All this three phase stuff makes me wonder if a car alternator (with diodes removed) would make a fair AC servo motor (you would have to supply the field) I guess one disadvantage is that they would have fairly high inertia The advantage of the separate field would be a wide constant power speed range (vary field roughly proportional to inverse speed) Peter Wallace Mesa Electronics ------------------------------------------------------------------------------ Centralized Desktop Delivery: Dell and VMware Reference Architecture Simplifying enterprise desktop deployment and management using Dell EqualLogic storage and VMware View: A highly scalable, end-to-end client virtualization framework. Read more! http://p.sf.net/sfu/dell-eql-dev2dev _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
