Re: Help, continuing to burn drives

Keith,

Be careful with how you place diodes to ground. You could set up
your own little ground loop circuit with different grounds on
equipment at different levels.

Jeff


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Keith Clark" <mail@t...>
wrote:

>
> Thanks Jon, I am not sure about the diodes, just looking into the
> idea.
> Keith
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...>

wrote:

> > Keith Clark wrote:
> >
> > >Yes Jon, it is me again with the same problem. I have gutted

the

> > >machine and am reworking everything. Plan to find the trouble
> one way
> > >or another. It looks like one problem is that the relay turning
> on
> > >and off the powersupply is on the DC side instead of the AC side
> and
> > >that might be causing spikes when I turn it on?
> > >
> > It causes a current surge, for sure. You are connecting a

massive

> capacitor
> > bank to a smaller, discharged set of capacitors in the drives,
> when the
> > relay
> > closes. The current is limited only by the resistance of the
> wires. If the
> > supply capacitors are at 75 V, and the wires have a resistance
> of .1 Ohms,
> > then the current will be 750 Amps when the contacts close. I
> imagine the
> > relay contacts can't survive this for long, either. The wires
> would have to
> > have a lot of inductance for there to be a voltage surge related
> to this.
> >
> > > Another change is to
> > >switch to unipolar wiring of the motors and drop to 5 amps with
> > >limiting resistors on the Gecko. Also some diodes on the Gecko
> side
> > >to ground.
> > >
> > Doides to ground? I've never heard of this on a Gecko. Where
> will you
> > connect
> > these diodes?
> >
> > > I already have them across the fuses which were no help
> > >before. I need to get systems to limit current and voltage
> installed
> > >to prevent those variations it looks like I am experiencing.
> > >
> > >I really think the y motor is ok since it is new but when
> everything
> > >has been redone and protected as much as possible, I will try
> your
> > >neon light test. Thanks again!
> > >
> > >
> > Even new motors can, possibly, be bad. It would be rare, of
> course, but
> > anything can happen.
> >
> > >Keith
> > >
> > >
> > >
> > >
> > >
> > >
> > >
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