Low budget plasma setup, what do I need?

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15 Jun 2019 03:43 #136943 by islander261
The stepper power supply voltage you need to get the published performance out of your steppers is the square root of winding inductance in mH times 32. You don't need much head room, the power supply numbers published by manufactures assume there will be some back emf. If you have large enough filter capacitors with bleeder resistors you are good to go with most any hobby sized system. Most people are surprised at the voltage required (this is actually pretty basic physics). When I changed the power supply and drivers to get closer to the required voltage I was amazed at the difference in acceleration it made. I actually made my plasma table accelerate so fast that the plasma arc couldn't keep up and went out! Tommy is the guru of low budget builds but you will be amazed of the performance of builds done when engineered from the ground up.

John

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15 Jun 2019 05:09 #136949 by rodw

tecno wrote: 48VDC is way too close to the 50VDC driver max voltage.


You may perceive that but there are thousands of machines out there running a 48v power supply with controllers with a peak volts of 50V, myself included. Many of the me are commercially built and sold machines.

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15 Jun 2019 18:12 #137001 by tecno

tommylight wrote: 36V is plenty, no worries there.
Anyway, pushing geckos at 50V is asking for trouble, back EMF could send them to heaven easily.
All the small ones I make use 24V, some only 19V from laptop power bricks.


This is exactly what I have found out years ago with theses small old type 250's

Anyhow, time will tell how bad they will run on 36V :woohoo:

Back to initial question as regards my scribble schematics = is there something missing?

Cheers
Bengt

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20 Jun 2019 19:07 #137411 by tecno

tecno wrote: As suspected = NOTHING

So now I have decided to step up a notch and as my primary goal is a AC/DC TIG with decent functionality such as low Amp start for very thin material.
This is what is on its way to me tiny.cc/04c07y



Built in 50 Plasma with Pilot Arc



The welder/plasma has landed today :)
Initial TIG test looks OK

The new Parker torch with current adjustment is very nice, now I need some hours of testing.
Attachments:

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20 Jun 2019 22:19 #137425 by tommylight
New toys ! Nice !

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21 Jun 2019 07:36 #137459 by tecno
Yes it is.
I sure hope my power lines can handle this power hungry beast.
Not yet tested flat out 200A AC/DC on aluminium.
Only 3-phase 16A and this is delivered with 1-phase 32A plug but now starting with a 16A 1-phase plug with lights flickering from the start surge but it welds OK at lower amps.

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22 Jun 2019 00:23 #137528 by tommylight
In DC mode that is not a problem, in AC mode that becomes a big problem.
I do have a 200A AC/DC tig, anything above 100A on AC will trip the breaker. This is at 220V, have not tested it at 380V yet.

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22 Jun 2019 00:58 #137533 by andypugh

tommylight wrote: I do have a 200A AC/DC tig, anything above 100A on AC will trip the breaker. This is at 220V, have not tested it at 380V yet.


Change the breaker. They have trip characteristics from A to D and then E, K, S, Z.

uk.rs-online.com/web/c/automation-contro...rcuit-breakers/mcbs/

(drop down the "tripping characteristics" filter.)

Try a D for an inductive load.

Video, slightly boring:

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22 Jun 2019 03:10 #137543 by rodw
I have a 200 amp MIG. I had similar issues when welding on single phase with light flickering and breakers tripping on a long weld becasue we had connect it to the nearest 20 amp house circuit.

Subsequently I upgraded the wiring so there was a 40 amp breaker at the main board and a single cable going from the main circuit board to a sub-board in the shed (that has almost as many breakers as my whole house!). The lights never flickered again!

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22 Jun 2019 04:12 #137550 by thefabricator03

rodw wrote: I have a 200 amp MIG. I had similar issues when welding on single phase with light flickering and breakers tripping on a long weld becasue we had connect it to the nearest 20 amp house circuit.

Subsequently I upgraded the wiring so there was a 40 amp breaker at the main board and a single cable going from the main circuit board to a sub-board in the shed (that has almost as many breakers as my whole house!). The lights never flickered again!


The company I manage the workshop for has a 100 amp 3 phase circuit feeding the whole premises. Our owner probably though it was overkill when he build our shed in 1987.

Today I have over twelve 350 amp MIG welders in the shed with other large equipment, Everytime our Ironworker powers up the lights in the shed dim. When I installed our 125amp plasma cutter I could not use it when my guys were welding or the main breaker would trip, I had it put on its own circuit and that stopped the problem,

The real solution is to upgrade our power supply, I have got quotes and they came back at the $150,000 mark.
I am waiting for the owner to retire so I can take over and make some hard decisions he does not want to do.

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