Re: [CAD_CAM_EDM_DRO] Re: Help, continuing to burn drives

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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