Powermax 125 Divided Arc Voltage 100:1

[34by151]

Im upgrading a plasma table from a Chinese plasma to a Hypertherm Powermax 125

The issue I have is the old plasma has an internal 100:1 voltage divider
The THC is a Fangling F1628S and as far as I can tell will only work with a 100:1 voltage divider

The Hypertherm has an internal 20:1 that feeds the voltage divider board
This then allows 20, 21.1, 30, 40 and 50:1

So I need to convert the Hyperthem to 100:1

I dont have an external voltage divider to use raw arc voltage
I can get one in but I'd prefer not to modify the hypertherm

As best I can tell the hyperthem internal 20:1 voltage divider is
100K/5K


This is connected to the CPC voltage divider


The 50:1 dip switch adds a 3K32 resistor in parallel to the 20:1

So 5K and 3K32 in parallel is 2K making the voltage divider 100K/2K = 50:1

So adding an external 2K across pins 5 and 6 on the CPC should make the ratio 100:1

5K,3K32,2K in parallel is 998.8 ohms
100K/998.8 = 100.12:1 (close enough to 100)

Anyway going to try this after the holiday break

[weldguy]

I am not an electronics guy so can't help but this topic interests me as I am not sure of the resistor should be placed between pins 5 and 6 or if the resistor just goes inline on pin 5. Hopefully an electronics guy will chime in here.

[34by151]

The Powermax 125 has an internal 20:1
The voltage divider board puts a resistor in parallel with one of the resistors in the 20:1 divider
This drops the value of the resistor increasing the ratio

So if you measure the resistance of pins 5/6 on 20:1 you will get 5K on 50:1 you get 2K

The chart only shows 20,30,40,50:1 but you can get 60,70, and 80 as well

60:1 = sw2 & sw4 on
70:1 = sw3 & sw4 on
80:1 = sw2, Sw3, Sw4 on

BTW on the past I have used a dual op-amp circuit to divide the voltage externally
Did this on the old 45 (not xp), I did not realise the internal divider was 50:1 not 20:1 on these units
I also used an op-amp on everlast and unimig as the internal dividers were not accurate values

On thing I do when commissioning a machine is to put my digital oscilloscope on the voltages
I put one channel on the raw arc voltage and one on the divided arc voltage
This allows me to tune the divider ratio.

Its a small point but it allows you to tune the THC to read the exact raw arc volts.
This makes it a lot easier to dial in materials as the thc will then read the same as book values

IE the powermax 50:1 is actually 51.1:1

[rick_b]

34by151 Can I ask, if the arc volts are wrong what sort of problems would you see?

[weldguy]

Great info, appreciate the response and enjoyed the read. Great idea to monitor raw and divided voltage for precise tuning. I’ve always said don’t matter the volt value, if the heights correct thats all that matters which is true but to be able to set it as per the charts would be ideal.

[34by151]

34by151 Can I ask, if the arc volts are wrong what sort of problems would you see?

Well there are 2 answers to that question

First, assuming the voltage divider ratio matches the THC
All you get here is a difference between the book value and your actual reading on the THC.
IE the cut chart says 100v and you read 105. So setting to 100 on the thc would make the torch low and produce a negative bevel
Now you can adjust you values as you dial in material or get the THC to read right and the cut charts will be just about spot on

Second answer
Assuming the voltage divider is off between the plasma and thc
What you will see is a varying difference in volts on the THC
Assuming it does not trigger an error on the THC you can dial in the volts to you material or fix the divider ratio
IE at 90v (raw) you may read 91V (thc). But at 130V(raw) it might only read 125, a non lenear relationship

[34by151]

Ran some tests today 2.04K in parallel with pins 5 and 6 is exactly 100:1
2K is 101.1, close enough

So a pair of 1K resistors in parallel with the pins 5 and 6 is perfect for a Chinese THC that needs 100:1 divided arc volts

[34by151]

Just for reference if you want an exact voltage
This is the circuit I use

The Op-amp buffers the divided arc voltage (no current draw)
The trimpot can then be adjusted to provide the ratio you need
This will work with a min of a 15:1 divided arc voltage on the plasma



You can use this to tune the voltage divider or provide the ratio you need
Assuming you have a 50:1 connected to you THC and the volts on the THC dont match the raw arc volts
You can use this to get them to match
If you do that the volts on the cut chart should match a perfect cut and you should not have to adjust your cut charts.

[weldguy]

Great info, thank you.

[SegoMan DeSigns]

Where is the Hypertherm reps response on this? It is on the Hypertherm link..

[rick_b]

I have a number of problems with a new machine that no one has been able to fix. One of the problems I have is the THC will not follow the steel when it bows, it follows it up but it never comes down the other side, so it can end up as much as 1” to 1 1/2” above the steel. Could the voltage divider being wrong cause this?

[34by151]

Where is the Hypertherm reps response on this? It is on the Hypertherm link..

As an extract from an email with Hyperthem Technical Services ,"The exact resistance to get 100.1 ratio from 50:1 ratio will be 2.04K ohms"
This was in a reply to my email asking for confirmation on my calcs. It came in after I ran my test and setup the customers plasma

[34by151]

I have a number of problems with a new machine that no one has been able to fix. One of the problems I have is the THC will not follow the steel when it bows, it follows it up but it never comes down the other side, so it can end up as much as 1” to 1 1/2” above the steel. Could the voltage divider being wrong cause this?

This could be a number of issues,voltage and THC settings come to mind
Does your thc have a "voltage protection value" setting, you may be triggering this
It might also be in your motor/stepper setup and Sensitivity setting

I sugesst you start a new thread and detail the full issue and your setup
IE plasma, controller, thc makes and models
Im sure we can all help you out

[SegoMan DeSigns]

Where is the Hypertherm reps response on this? It is on the Hypertherm link..

As an extract from an email with Hyperthem Technical Services ,"The exact resistance to get 100.1 ratio from 50:1 ratio will be 2.04K ohms"
This was in a reply to my email asking for confirmation on my calcs. It came in after I ran my test and setup the customers plasma

I'm glad they got back with you, I miss Jim Colts and his wisdom he shared on this site.

[34by151]

I'm glad they got back with you, I miss Jim Colts and his wisdom he shared on this site.

I actually had a response on boxing day which is great. Im in OZ so I cant comment on the US support but I have no complaints with Technical Services
Oceania

[rick_b]

I have a number of problems with a new machine that no one has been able to fix. One of the problems I have is the THC will not follow the steel when it bows, it follows it up but it never comes down the other side, so it can end up as much as 1” to 1 1/2” above the steel. Could the voltage divider being wrong cause this?

This could be a number of issues,voltage and THC settings come to mind
Does your thc have a "voltage protection value" setting, you may be triggering this
It might also be in your motor/stepper setup and Sensitivity setting

I sugesst you start a new thread and detail the full issue and your setup
IE plasma, controller, thc makes and models
Im sure we can all help you out

Thanks for the information. The machine is all Hypertherm, controller, plasma, and THC with Mitsubishi Electric's SERVO and drives. if I don't get anywhere next week after the tech looks at it I will try starting a new thread for it.

[Paranoid]

I realize after I purchased a THC Fangling F1621 that it requires a 100:1 ARC voltage input. I have a Hypertherm 45xp that can set ARC voltage to a 50:1
Can you provide a wire diagram as how I need to wire the resister in the circuit? Maybe a picture of how you did it? Thanks so much, I am in the process of building my own CNC table and still at the bottom of the learning curve.

[Paranoid]

Are you sure that the Faglin required a 100:1 and that it was actually looking for raw voltage and had its own divider of 100:1 built in?

[weldguy]

Tried to determine if it required raw voltage input and has an internal divider, or if you need to supply it with a 100:1 signal. The manual is pretty weak and never really defined that however it does appear as though there may be a separate voltage divider box. Did you buy your unit new?

[Paranoid]

Initial appearance that it has a built in voltage divider. It is a new unit. Very poor manual and support is weak. I asked if I need raw voltage or it it will accept the voltage as 50:1
The response was a diagram of the circuit board and a message that states "Open the box and turn the switch on to change the simulated 1:100 to 1:50." I have not yet opened up the box. Will update when I open box to see.

[Paranoid]

Can anyone agree that turning ON the switch would allow the input from the Hypertherm 45xp ARC output divider that I have set to 50:1
Or does this make only internal voltage division inside the unit? Documentation really sticks on this unit, should have done some more research.

[weldguy]

I would guess that since they have 2 options selectable with a dip switch that its expecting divided voltage not raw. If it was accepting raw voltage for internal division there would be no reason to have a selection option but i’m no chinese electronics wiz.

[34by151]

I haven't tried that on the F1620 however the F1628S had the same thing and it did not work
The only thing that worked was to leave it on 100:1 and set the hypertherm to 100:1

To do this Hypertherm voltage divider is set to 50:1 with a 2k resistor on pins 5 and 6 of the cpc cable

For reference if you want exactly 100:1 the resistor value is 2.04K
2K is 101.1 which is close enough

[weldguy]

I haven't tried that on the F1620 however the F1628S had the same thing and it did not work
The only thing that worked was to leave it on 100:1 and set the hypertherm to 100:1

To do this Hypertherm voltage divider is set to 50:1 with a 2k resistor on pins 5 and 6 of the cpc cable

For reference if you want exactly 100:1 the resistor value is 2.04K
2K is 101.1 which is close enough

Great info, hopefully the other member sees this. Thanks for chiming in.

[s936083]

According to what I know, F1628S has a built-in 100:1 voltage divider. Hypertherm needs to output the original arc voltage. Does your THC not have a built-in voltage divider?