On 2/13/2013 12:05 AM, Gene Heskett wrote: > On Wednesday 13 February 2013 00:00:37 Dave did opine: > > >> On 2/12/2013 10:47 PM, Gene Heskett wrote: >> >>> On Tuesday 12 February 2013 22:36:22 Przemek Klosowski did opine: >>> >>>> On Tue, Feb 12, 2013 at 10:57 AM, Dave<[email protected]> wrote: >>>> >>>>> I have a large CNC lathe that has contactors wired in between the >>>>> servo drives and the motors and on an Estop, the contactors drop out >>>>> and the 3 phase servo motor windings are shorted together to stop >>>>> the motors. >>>>> >>>> I thought this is a no-no---opening of the circuit causes the servo >>>> driver stage to abruptly change from high-current to zero current >>>> flow, bound to cause transients in every inductance in the system. >>>> THere's a standard warning for the people rewiring their equipment >>>> with VFDs to take the reversing drum switch out from next to the >>>> motor, and replace it with something that commands the VFD to >>>> reverse. >>>> >>>> Is it one of those things that shouldn't be done routinely but is OK >>>> in an emergency? >>>> >>> Generally its a big "no" on that. The VFD probably assumes there is a >>> motor out there, and using a switch to interrupt would be a bit hard >>> on it because the average switch breaks dirty, going on& off for 5 >>> to 10 milliseconds, and re-closing the switch at an unknown position >>> in the VFD's output sequence stands a very good chance of letting the >>> magic smoke out of it, and we all know things don't work without that >>> magic smoke. Do ALL your starting and stopping via the input >>> controls on the VFD, so that it can handle the sequences properly. >>> >>> This is also true for stepper drives. The most solidly connected >>> wires in the system should be between the motor and the driver. A >>> flaky connection there will blow the tops off the chips in the >>> driver. Instantly in terms of human time. >>> >>> Cheers, Gene >>> >>> >>>> I thought this is a no-no---opening of the circuit causes the servo >>>> driver stage to abruptly change from high-current to zero current >>>> flow >>>> >>>> Generally its a big "no" on that. The VFD probably assumes there is a >>>> motor out there, and using a switch to interrupt would be a bit hard >>>> on it >>>> >> That is what I thought also.. however that is the way that lathe is >> wired. It uses Siemens servo drives for the feeds and the spindle and >> the drives are original. >> >> I would not recommend doing that to any random servo drive, but it seems >> to work with these Siemens drives. >> >> Dave >> >> > And they were designed which side of Fred& Wilma Flintstones wedding? > > Sorry, just couldn't resist, sometimes this stone age stuff turns out to be > pretty tough. > > It had to be when Barney Rubble was turning the cranks. ;-) > > I'll get me pj's& toddle off to bed now... > > Cheers, Gene >
They aren't That old! 1992 Vintage. Not too long after the wheel was invented and well after the creation of "dirt". So they aren't older than dirt. ;-) Siemens made very similar servo drives up until about 2000, but they changed the packaging. Dave ------------------------------------------------------------------------------ Free Next-Gen Firewall Hardware Offer Buy your Sophos next-gen firewall before the end March 2013 and get the hardware for free! Learn more. http://p.sf.net/sfu/sophos-d2d-feb _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
