RE: [CAD_CAM_EDM_DRO] Re: gecko burned again

RE: floating ground detection...

Measure the voltage between -DC and ground using a digital volt meter. The
voltage should be zero. If the voltage wanders around, it's floating. If
you use an old fashion analog meter you can ground it by testing due to the
low impedance of the meter. Alternatively, when all power is off and the
cap is fully discharged, measure continuity between -DC and ground, there
should be a connection there and low resistance. Sometimes people ground
the +DC side, that works just as well.

Floating grounds can wander high and create a voltage differential that
exceeds the insulation capability of the power bridge. Fuses have a
statistical chance of working, I don't know any mfgr that will guarantee
their drive will survive the sort of current surge that is needed to take
out a fuse unless there is some serious inductance in line which slows the
current rise rate. Even the $5000 servos from Rockwell, Siemens, or
Indramat can be taken out by a dead short at the motor.

Greg

> -----Original Message-----
> From: Keith Clark [mailto:mail@...]
> Sent: Sunday, November 07, 2004 12:26 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: [CAD_CAM_EDM_DRO] Re: gecko burned again
>
>
>
>
> How do I figure out if I have floating grounds?
>
> The power supply is new and I don't think it is causing the
> problem. Seems there is no machanical problem apparent. I guess
> rewiring could be helpful to be sure there are no bad connections...
>
> Thanks
> Keith
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "john labutski" <kd6wd@c...>
> wrote:
> > You might also start looking for a mechanical problem as well. It
> could be
> > cooling to the Gecko, possibly binding in the y axis on the mill,
> moisture
> > getting into the control box, floating grounds. If your using a
> linear
> > power supply, sometimes the windings short out due to age and heat
> and you
> > end up with a different voltage coming out of them. A lower
> voltage means
> > higher current.
> >
> > Don't know if this helps but its some food for thought.
> >
> > John
> >
> >
> > ----- Original Message -----
> > From: "Keith Clark" <mail@t...>
> > To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> > Sent: Sunday, November 07, 2004 9:56 AM
> > Subject: [CAD_CAM_EDM_DRO] gecko burned again
> >
> >
> > >
> > >
> > > Well, the y axis gecko drive burned again this morning. This
> time
> > > there are no loose wires. I was doing very little with the
> machine
> > > and had just turned it on when during a y axis G0 move, the drive
> > > burned up. I assume this is an indication that the Gecko cannot
> > > handle the motor I am using. This is an old topic and I have
> asked
> > > for help with this problem before. The mill is a Bridgeport
> Series
> > > 1 CNC originally controlled by Boss 6 but now using Anaheim Nema
> 42
> > > high torque stepper motors and Mach2 software with a Campbell
> > > breakout board.
> > >
> > > At this point is seems reasonable to try another brand drive?
> > >
> > > Thanks
> > > Keith Clark
> > > clarkfamily5@c...
> > >
> > >
> > >
> > >
> > >
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> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:
> aol://5863:126/rec.crafts.metalworking or go thru Google.com to
> reach it if you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider this
> to be a sister site to the CCED group, as many of the same
> members are there, for OT subjects, that are not allowed on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY
> POSTING THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO
> EXCEPTIONS........
> bill
> List Mom
> List Owner
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>
> Yahoo! Groups Links
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