Well guys, all good medicine here. I especially like the idea of a button
or a key switch that can be used in the situation following an estop limit
trip to allow the drives to be reenergized and jog off the limit switch. I
can certainly learn to use the soft limits and if I can figure out a way to
home everything with or without a dedicated home switch it is all good.
Its so crazy it just might work LOL....
I am sure I will have tons more questions for you guys as I Wade into
this deep water here and hopefully with your help I won't wind up in the
fetal position at the bottom of the lake trying to breathe water like they
did in that movie I saw one time LOL....any further suggestions about this
particular subject fire away...peace
Pete
On Wednesday, February 13, 2013, Gene Heskett <ghesk...@wdtv.com> 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
> --
> "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>
> Intel Inside, Idiot Outside.
> I was taught to respect my elders, but its getting
> harder and harder to find any...
>
>
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