Interesting so using a relay to depower the vfd is bad junior then...using the controls computer estop and the mesa to shutdown the drive is a better option then.....that's good I was just looking at having to buy a larger relay for the spindle drive. Any input on the best way to accomplish this? Peace
Pete On Tuesday, February 12, 2013, Gene Heskett <[email protected]> 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 > -- > "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> > Hollywood is where if you don't have happiness you send out for it. > -- Rex Reed > 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 > [email protected] > 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! Learn more. http://p.sf.net/sfu/sophos-d2d-feb _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
