you guys crack me up!! ;<) peace Pete
On Wed, Feb 13, 2013 at 11:18 AM, Gene Heskett <ghesk...@wdtv.com> wrote: > On Wednesday 13 February 2013 11:06:18 Dave did opine: > > > 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<e...@dc9.tzo.com> 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 > > I shouldn't let my sense of humor out to play without a chaperon. :) > > A couple times recently I have been accused of being older than dirt. > Since I can't do anything about my birthday,I may as well poke fun at it as > long as I can. :) > > Hell, even the reference to Fred & Wilma dates me, I haven't seen a > Flintstones program on tv in a good 30 years, so I know there are folks on > this list who don't have a clue about them, or Howdy Doody either for that > matter. Magic twanger? Whazzat? ;-) > > Cheers, Gene > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author) > My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! > My views > <http://www.armchairpatriot.com/What%20Has%20America%20Become.shtml> > Your supervisor is thinking about you. > I was taught to respect my elders, but its getting > harder and harder to find any... > > > ------------------------------------------------------------------------------ > 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 > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ Free Next-Gen Firewall Hardware Offer Buy your Sophos next-gen firewall before the end March 2013 and get the hardware for free! 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