I think what Gene is saying is that a relay or contactor between the VFD and the motor is bad (likely to damage the VFD). The proper way for an E-stop condition to remove power from the motor is by switching off the power leading into the VFD. As you mentioned, your Teco VFDs have two power inputs, one for the motor power and another to power the logic. Leave the logic powered, and remove power from the power input that supplies power to the motor. The VFD should detect that loss of motor power and set a fault condition. Heck, it might even be smart enough to short the motor windings to stop the motor more quickly.
BTW - In the debate between using the E-stop to remove power and coast the motors, or actively control the VFD to quickly stop the motors, I generally fall on the side of powering down the VFD and coasting to a stop. Yes, a powered shutdown stops the motor more quickly, but the entire point of an E-stop is to shut down motion when the controls have gone awry. Using possibly faulty controls in the hope of a controlled motor halt seems problematic to me. If nothing else, it's conceptually complex. I want an E-stop to be as simple and reliable as possible. If I need faster, I'll put a brake on the back motor shaft and have the E-stop release the brake to stop the motor. E-stops are hardwired. If it needs firmware in a VFD micocontroller, or PLC ladder logic, or CNC code running on a PC... it's not an E-stop. YMMV. On 02/12/2013 10:57 PM, Pete Matos wrote: > 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 > > ------------------------------------------------------------------------------ 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
