HF Start & DM556 Drives?

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30 Jun 2021 19:44 #213359 by mkardasi
I'm curious if anyone has used the StepperOnline DM556T or DM342T drives on a plasma table with a HV/HF start supply?

My table currently uses a G540 and I had to add a RF shield around the hand torch & lead to keep the G540 from faulting out when plasma fires. The drawback is this added a lot of bulk and heft to the torch & leads. I've dealt with it for a few years but now I'd like to reduce the bulk If I could. Replacing the G540 with drives that tolerate EMI much better & removing the shielding off the torch would be my ideal solution. 

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30 Jun 2021 21:39 #213380 by tommylight
Replied by tommylight on topic HF Start & DM556 Drives?
I have used and still use everything from cheap stepper drives to very expensive ones and servo drives, almost always with HF/HV start plasma sources.
That requires much more than just shielding the torch wire, first and foremost having proper grounding, meaning all grounding and shields go to the same spot in the cabinet in a "star" formation, never daisy chaining,
-using shielded wires for everything if possible
-connect the shield ONLY on the cabinet side, leave the other side unconnected
-shielded motor wires are also nice to have, shield should also be screwed to the motor (not motor mount)
-RF filtering on the power input
-signal cables as short as humanly possible
-all machine cables as far as possible from the torch cable and the plasma source.
More info here
forum.linuxcnc.org/plasma-laser/35349-cn...fo-and-guide?start=0
forum.linuxcnc.org/plasma-laser/38974-di...rything-in-one-place
and in case you have some spare time:
forum.linuxcnc.org/show-your-stuff/38547...plasma-build?start=0

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30 Jun 2021 22:06 #213389 by mkardasi
Replied by mkardasi on topic HF Start & DM556 Drives?
Thank you. Have you specifically tested a G540 drive against the methods proposed above?

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01 Jul 2021 03:16 #213410 by BeagleBrainz
What Tommy suggest is just general best practice. Something you’d find in most articles, manuals and other literature.
It really won’t matter what actual components you use. The idea is to try and minimise electrical noise.
You’ll find working with those suggestions your installation will end up neater and easier to modify or diagnose in the future.
The following user(s) said Thank You: tommylight

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06 Jul 2021 08:34 #213834 by vre
Replied by vre on topic HF Start & DM556 Drives?
Mine plasma source (nertajet HP) has a patent that initiates arc without HV-HF
this patent is to inject little argon gas for starting arc.
Argon has lower breakdown voltage than air so arc starts with lower voltage and without HF after arc is started argon stops and cuts with air/o2/n2 etc
so not consuming argon for cuting..

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