On 01/24/2017 03:54 PM, Greg Bernard wrote: > Seeing the discussion of servo vs. stepper solutions come up once again I > wonder if anyone has had experience with these: > http://www.automationtechnologiesinc.com/products-page/nema34-closed-loop-stepper-motor-system-hybrid-servo-kit/nema-34-hybrid-servo-motor-kl34-8n-1000-rated-torque-1128-oz-in > They are only step/dir but they are being used in both Tormach and Shopbot > machines which leads me to believe they are a cost-effective > middle-ground.Any thoughts? > Well, if you are going to go the whole closed-loop route, why do it with a high pole-count stepper motor? A 2-phase stepper needs 8 transistors, and you need high driving frequencies to spin it fast. A 3-phase brushless motor typically has 4-8 poles, so the frequencies are much lower. (200 full step/rev steppers have 50 poles.) And, the 3-phase drive only needs 6 transistors. The stepper motor still has the resonance issue, even though the drives are set up to not excite it, the resonance is still there. The lower pole-count brushless motor moves it down to a point where it is rarely a problem.
So, I really don't see the advantage to the closed-loop stepper. Automation technologies has quite affordable brushless servo motors, too. Jon ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
