Plasma C Wiring

snowgoer540
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16 Dec 2020 12:20 #192129 by snowgoer540

Replied by snowgoer540 on topic Plasma C Wiring

tommylight wrote:
That will be 8.4V at the THACD10 input when plasma is at 140V, soooo that is very good.

Can you walk me through that calc? I definitely don't follow (wanting to learn something new here, not questioning the data

)

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tommylight
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16 Dec 2020 12:46 #192131 by tommylight

Replied by tommylight on topic Plasma C Wiring

Open circuit voltage 300V = 18V at the port after divider
cutting voltage 139V = 8.4V at the port or THCAD10
300/139=2.15827
18/2.15827=8.339

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snowgoer540
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16 Dec 2020 13:39 #192133 by snowgoer540

Replied by snowgoer540 on topic Plasma C Wiring

tommylight wrote:
Open circuit voltage 300V = 18V at the port after divider
cutting voltage 139V = 8.4V at the port or THCAD10
300/139=2.15827
18/2.15827=8.339

Thanks Tommy.

I would have thought that that the cutting voltage of 139V would be 6.95V at the port (139/20 = 6.95).

It might appear I've been doing it wrong?

I'm further confused because the offsets and what not use the ratio as the multiplier to get back to the full scale voltage.

I must be missing something? :unsure:

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tommylight
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16 Dec 2020 17:35 #192148 by tommylight

Replied by tommylight on topic Plasma C Wiring

snowgoer540 wrote:

I would have thought that that the cutting voltage of 139V would be 6.95V at the port (139/20 = 6.95).

That is correct, also, but you mentioned that the max voltage at the port is 18, so i used that as a reference.

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rodw
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16 Dec 2020 20:23 #192178 by rodw

Replied by rodw on topic Plasma C Wiring

I'm more with snowgoer on this one. Stating it another way. Hypertherm say that the voltage on the divider will never exceed 18v. Maybe it is clamped off at that level in some way. We don't know.

But with a 20:1 divider, 18 * 20 = 360V

I think 300 volts will be exceeded on piercing or on void crossing. I know my plasma cutter will occasionally go to its full scale of 300 volts and beyond.

Either way, its not a concern for us due to the overvoltage capacity of the THCAD. The 18 volt limit is not a concern as it won't fry our circuit.

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tommylight
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16 Dec 2020 20:31 #192184 by tommylight

Replied by tommylight on topic Plasma C Wiring

None of that matters, if the voltage goes above the set point the THC will already be adjusting the height, no matter how high the voltage is.
I asked only to confirm that there is some headroom for adjustments.
Example, if the plasma/divider/THCAD are set so that 120V is the maximum the THC can read, ( not a real case, this would need a 1:12 divider on a THCAD10 ) there is no room for going higher if need be.

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rodw
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16 Dec 2020 21:11 #192196 by rodw

Replied by rodw on topic Plasma C Wiring

tommylight wrote:
None of that matters, if the voltage goes above the set point the THC will already be adjusting the height, no matter how high the voltage is.

Only if the THC is enabled. The big peaks are typically when the THC is disabled and are therefore ignored.

Probably the main thing to be aware of is that there needs to be enough headroom for a void crossing event to be detected. It the maximum while cutting by the specs is 140 volts, then 200 volt full scale is probably close to perfect!

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snowgoer540
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17 Dec 2020 01:29 #192214 by snowgoer540

Replied by snowgoer540 on topic Plasma C Wiring

Ok, I'm tracking. Always looking to soak up some new knowledge, just wanted to make sure I wasn't missing something.

Sorry to hijack the thread haha, enjoy this star wars quote as apology :laugh:

*these aren't the droids you're looking for*
*these aren't the droids we're looking for*
*he can go about his business*
*you can go about your business*
*move along*
*move along, move along*

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tommylight
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17 Dec 2020 13:01 #192246 by tommylight

Replied by tommylight on topic Plasma C Wiring

*jedai busines, nothing to see here *

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