Re: Help, continuing to burn drives

--- 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
> >
> >
> >
> >
> >
> >
> >
> >Addresses:
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