On 4 June 2013 08:23, propcoder <[email protected]> wrote: > What reasons are for using hall sensors? As I understand, commutation > goes from software, which means there is no difference between qi or qh > modes in reaction time.
With Hall sensors the motor works at full torque at switch-on. With q and qi modes it needs to perform an alignment process. q is OK for a spindle, but can't be used reliable on an axis that is under load. qi mode might be usable for an axis, if random movement during the alignment is acceptable. > I was planning to spin my 8-pole BLDC motors up to 3000rpm. This means > 5ms every electric cycle. When using 1ms servo period, this may be not > very nice.. What do you think? I think I will need to try smaller servo > periods. Hall commutation only changes state 6 times per electrical cycle, so you will end up with something similar. If you can run a 500us servo thread then that would be nicer. > I thought all this hostmot2 and bldc on 5i23 + 7i39 commutates in > hardware (I think this is possible). I am disappointed a bit. It is possible, and there are drives out there that take hall signal inputs and commutate in hardware. There are also AC servo drives that take encoder inputs, but they tend to be a _lot_ more expensive than the 7i39, and generally require a matched absolute encoder. -- atp If you can't fix it, you don't own it. http://www.ifixit.com/Manifesto ------------------------------------------------------------------------------ How ServiceNow helps IT people transform IT departments: 1. A cloud service to automate IT design, transition and operations 2. Dashboards that offer high-level views of enterprise services 3. A single system of record for all IT processes http://p.sf.net/sfu/servicenow-d2d-j _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
