Advice THCAD

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21 May 2020 20:33 - 21 May 2020 20:37 #168527 by aleksamc
Advice THCAD was created by aleksamc
Mesa has THCAD -5, -10, and -300.

As I understand, if have manual simple plasma generator (there is no dividers in it), I must use THCAD-300 and connect to this device directly to high voltage?
What maximum voltage it supprots? Will it not be dameged with high voltage picks?

What does mean this sentence from datasheet of THCAD:
"The 300V version of the THCAD has all input divider resistor on board and can connect directly to the plasma voltage of touch start type torches only"

What does "touch start type torch"? I'm very new to plasma.
Last edit: 21 May 2020 20:37 by aleksamc.

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21 May 2020 20:45 #168529 by PCW
Replied by PCW on topic Advice THCAD
It means the THCAD-300 is not suitable for high frequency start torches
(at least without tapping into the plasma voltage _before_ the HF start transformer)

The voltage at the torch can be as high as 20-30KV when starting with HF
start plasma

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21 May 2020 20:48 #168530 by tommylight
Replied by tommylight on topic Advice THCAD

What does "touch start type torch"? I'm very new to plasma.

Scratch start plasma, the ones without pilot arc, so the torch needs to be dragged through the material for it to start cutting.
-
WARNING : below info is not from Mesanet, and they do not advise on using THCAD300 for HF/HV start plasma cutters as any miss wiring or wiring it to output terminals of the plasma source will most probably damage the THCAD

THCAD300 can be used with all plasmas, BUT it can not be connected directly to the clamp and torch terminals as that would send over 20000V to it.
It has to be wired directly on the rectifier output!
I am sure it works with HV start as i have one in use for several months. No tests yet on HF/HV start as i did not get the THCAD i ordered yet, they are still quarantined in Switzerland ! :)

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21 May 2020 21:03 #168532 by PCW
Replied by PCW on topic Advice THCAD
Here's a nice photo of the result of connecting a THCAD-300 directly to the torch terminals
of a HF start torch:

forum.linuxcnc.org/forum/search?query=TH...&start=435#gallery-3
The following user(s) said Thank You: tommylight, rodw

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21 May 2020 21:18 #168536 by tommylight
Replied by tommylight on topic Advice THCAD

Here's a nice photo of the result of connecting a THCAD-300 directly to the torch terminals
of a HF start torch:

forum.linuxcnc.org/forum/search?query=TH...&start=435#gallery-3

I think i saw that picture before, wonder where...... :)

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21 May 2020 21:44 #168545 by aleksamc
Replied by aleksamc on topic Advice THCAD
Wow, so many answers, thanks you a lot.

So, when plasma starts, in parallel to main power connects high voltage transformer. I need to open plasma, found there rectifier (Plasma has IGBT transistor) and to connect to it?
Or, If I connect THCAD after start of the torch, with help with contactor, it will work fine?

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21 May 2020 22:51 #168548 by tommylight
Replied by tommylight on topic Advice THCAD
Here is one example of an IGBT inverter plasma, just for reference:
forum.linuxcnc.org/plasma-laser/36837-ne...ion?start=170#148131
You can post pictures of the inside of the plasma, we can try to figure out where to wire it.

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21 May 2020 22:59 #168549 by PCW
Replied by PCW on topic Advice THCAD

Or, If I connect THCAD after start of the torch, with help with contactor, it will work fine?


assuming you have a contactor rated for 25-30 KV, yes :-)
The following user(s) said Thank You: tommylight

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21 May 2020 23:09 #168550 by tommylight
Replied by tommylight on topic Advice THCAD

Or, If I connect THCAD after start of the torch, with help with contactor, it will work fine?


assuming you have a contactor rated for 25-30 KV, yes :-)

LOL
That would set him back some pretty money ! :)
And would most probably be bigger than the plasma itself !

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21 May 2020 23:18 #168551 by aleksamc
Replied by aleksamc on topic Advice THCAD
LOL, it's very funy decision with contactor.)))

For current stage, It's defined, that thcad suits me complitly and I must to install it inside the plasma box.

Thanks for your answers.
When I will start connection of all boards, I will return to this topic and ask where to connect my board.

Who knows, mesa is make shipments now? What situation with quarantine now in that places?

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