On Sat, 29 Mar 2014, Florian Rist wrote: > Date: Sat, 29 Mar 2014 23:02:03 +0100 > From: Florian Rist <fr...@fs.tum.de> > Reply-To: "Enhanced Machine Controller (EMC)" > <emc-users@lists.sourceforge.net> > To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> > Subject: Re: [Emc-users] BLDC Servo Torque Problem? > > Hi Peter, > thanks for you reply. > >> Its hard to tell with motor specifications, sometimes they are RMS and >> sometimes they are DC (for example lots of large BLDC motors are rated 320V >> which actually means they are 220V AC motors) > > I see. I'll stick with 24 V for now, the power supply is a 350 W unit. > >> 1. initial rotor alignment (if wrong you will have different torque each >> direction) > > I think this is OK, as the motors spin smooth and nice in both directions. > >> 2. Make sure the deadtime is set to 0 > > It is set to 0 (line 207 of the hal ini: http://restweiss.de/bldc_1.zip). > >> 3. Make sure the PWM rate is set fairly high so you dont get current limiting >> from ripple current (40KHz is good for 7I39s) > > PWM frequency (is that PWM rate) is set to 20 kHz, but I tried 40 kHz > and it makes no difference. > >> 4. Make sure you have the 7I39 current limit set to 15A and not 7.5A > > Current is limited (still default setting) but I don't think this is the > problem. Using a clampmeter I measure 600 mA max. at stall.
Where did you measure the current? (you may indeed measure 600mA in the power leads with current limiting (7.5A) in the driver) If you see a red LED light on the 7I39, you have reached the current limit Another thing to check is that you have not somehow limited the max PWM value so you are not getting sufficient drive voltage (PWM does not get near 100% or near 0%) > >> 5. If you have problems at high speeds, consider running LinuxCNC master and >> raising the servo thread rate as high as you can (good MBs can do 4 KHz or >> better) (linuxcnc master has a patch to BLDC than extrapolates the >> commutation >> angle base on velocity so approximately halves the commutation angle >> error at high speeds) > > Oh, that's cool feature, but I only need very low speeds - so no need to > switch I guess. > > > What's next to investigate? > > Greetings > Flo > > ------------------------------------------------------------------------------ > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > 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. ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
