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### Author Topic: Question on Plasma THC control to users of this facility  (Read 8223 times)

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• 43
##### Re: Question on Plasma THC control to users of this facility
« Reply #20 on: November 26, 2016, 03:32:11 PM »
I did have trouble with the controllers, I could blow then very easily, that was sorted by making my own filter network on the motor cables using back to back diodes, MOV's and caps.  Also removing some earth loops I had placed on the system by trying to earth anything I could.

Not blown a chip since.

Not the same board as you link to there, but probably similar.

fuzzy picture here it sits in an extruded aluminium box.

I have extraction, used for welding.

#### robertspark

• 596
##### Re: Question on Plasma THC control to users of this facility
« Reply #21 on: November 26, 2016, 03:55:30 PM »

I will have a read through the information you have provided, yes I have the manual for mine rated voltage is 100 Volts in the user guide.

The input is 4.7KVA at rated output of 40 Amps, so really wants a 22Amp supply but duty cycle is 60% at that those figures.

I need to run the machine under 25 Amps if I can reasoning is it is on a 13 amp socket.

220 Volts x 13Amps = 2860 KVA * 0.85% efficiency I have 2431 KVA available, 100 Volts rated so around 24 amps cutting current.

I can push a bit higher but the garage supply which is really only rated at 20 Amps has to power PC, lights and a compressor.

Thanks for the rest of the information I will read through the posts you have listed, thanks for that.

UK is 230v

100v(OP) x 40A(OP) = 4kW (OP)
4kW / 0.85 (%eff) = 4.7kW [so that checks out]
4.7kW / 230v = 20.4A

You can probably get away with a 16A BS60309 plug and socket [I do with my powermax 45 (45A @ 132V, 0.99 power factor = 5,940kW), 6kVA at 25A generator recommended]
http://www.toolstation.com/shop/Electrical/d190/Industrial+Connectors/sd2430/Industrial+Plug+IP44/p36175
http://www.toolstation.com/shop/Electrical/d190/Industrial+Connectors/sd2430/Industrial+Socket+IP44/p20698
advantage is that they aren't fused .... so have a bit more give than a 13A plugtop.
looking at another 3A per 1hp for the compressor (approx),

duty cycle is the operating time per 10 min duty cycle (hence 60% duty cycle means 6 mins run time, 4 mins cooloff).

on a 20A mcb, you can probably get away with around 30A maybe a little more at that duty cycle depending upon breaker or fuse type..... also you'll find that your actual cut time probably won't be 6 mins anyway (as that would be ~ 5m of cutting at your feedrate.... continious on a small table..... not really possible in my opinion
http://wiki.diyfaq.org.uk/images/d/d4/Curve-MCBTypeB.png
http://wiki.diyfaq.org.uk/images/thumb/d/d6/Curve-MCBTypeC.png/640px-Curve-MCBTypeC.png

I was told by a hypertherm technical person that as a guide (starting point) if you've got the feedrates for 40A, and reduce the ampage to say 32A (20% reduction), then your feedrate should drop by a corresponding percentage (roughly).
Rob

Albert Einstein ― “If you can't explain it to a six year old, you don't understand it yourself.”

• 43
##### Re: Question on Plasma THC control to users of this facility
« Reply #22 on: November 26, 2016, 05:33:52 PM »
Uk is in theory  240 Volts + 6% and - 10%, http://www.schneider-electric.co.uk/en/faqs/FA144717/

but the voltage drop along my garage supply run gives me around 220 to 225 Volts when I have the plasma going and compressor running as well, it is not attached to the house.  The supply has two 20 Amp breakers in line, one in the house and another in the garage and yes I can trip it out. especially when I have the plasma up at around 40 amps cutting, lights on in the garage and the compressor kicks in (2HP)

Max time running was when I was cutting a butterfly out and that was 13mins run time in 2mm steel, granted not all cutting I know.

So I try to keep the cutting amps down, no matter what calcs  you wish to run.

I need to visit the local electronics shop in the morning and pick up some multi-pin sockets and 1mH inductors and drill/fit to the plasma, then I can box that back up and get it back in the garage.

I will run a modified G-code file and have a play with the home made THC driven from a PSU just to simulate things before I get too adventurous.

« Last Edit: November 26, 2016, 05:36:11 PM by AdrianH »

#### robertspark

• 596
##### Re: Question on Plasma THC control to users of this facility
« Reply #23 on: November 26, 2016, 05:39:57 PM »
Nice butterfly, you did that with a cut40?
Rob

Albert Einstein ― “If you can't explain it to a six year old, you don't understand it yourself.”

• 43
##### Re: Question on Plasma THC control to users of this facility
« Reply #24 on: November 26, 2016, 05:49:31 PM »
Yes that is with my cut40 and cnc.

Approx 270mm wide 220mm tall.

« Last Edit: November 26, 2016, 05:54:10 PM by AdrianH »

#### mc

• 380
##### Re: Question on Plasma THC control to users of this facility
« Reply #25 on: November 26, 2016, 06:50:16 PM »
Just had a quick scan through the thread on mig-welding. Are you the Adrian H who happened to sell a rapid cycle Harrison mill a number of years ago?

The basic older TB drivers are not great. They're ok if you don't push them near their limits, but lots of implementations have woeful heatsinking, which compound their limitations. For not much more money, I'd buy some newer individual TB6600 drives (search ebay for TB6600 - there are plenty options), which use far better chips, and would allow you to run a higher voltage power supply. You also get the benefit that if you do blow one up, you only need to replace that one.
For plasma, you need speed, and the main way to get speed from steppers is by increasing the power supply voltage.

• 43
##### Re: Question on Plasma THC control to users of this facility
« Reply #26 on: November 26, 2016, 09:08:19 PM »
Yes to the first question, a Mill I bought not really knowing what it was,  Had the switches but no feed motor if my memory is correct. I had, and still have a Harrison manual mill.  So went back to the manual mill. far less of an issue, only just getting it power driven now!

Why did you buy it from me?
I will have to stick to the controller for the time being it is all built in a box an all with a dedicated 24Volt PSU.

« Last Edit: November 26, 2016, 09:12:51 PM by AdrianH »

#### mc

• 380
##### Re: Question on Plasma THC control to users of this facility
« Reply #27 on: November 27, 2016, 08:06:40 AM »
I was going to convert it to CNC, but after much deliberation, I got the chance of a CNC lathe, then an even bigger mill, which led to another CNC lathe, which led to a ready to run CNC mill, and am currently retrofitting yet another mill.
In amongst that, the mill I bought from you got sold (I think I still have the wiring diagram from when I worked out exactly how the rapid cycle worked). I still have my original Harrison mill, which is currently setup to do second ops.

You could increase the supply voltage to your existing driver, however you really want to be using a linear supply.
I suspect the real reason you kept blowing controllers, was under deceleration, the drive dumps energy back into the power supply. Switch mode power supplies generally don't like that and have little capacity to absorb it, with the result you see a voltage surge, which and the TB chips just don't handle going over their rated voltage. Linear supplies on the other hand, with a reasonable sized capacitor will quite happily absorb the surge.
The other option is to add in a reverse energy dump, which will dump any energy from the drive into an external resistor (check the stepper motor basics guide over on gecko drive for examples)

#### robertspark

• 596
##### Re: Question on Plasma THC control to users of this facility
« Reply #28 on: November 27, 2016, 08:29:50 AM »
http://www.vigortronix.com/Toroidal.aspx

Buy direct from a manufacturer... you'll see their products resold via a numner of outlets (farnell, maplin, etc etc).

Adam is very helpful (and works odd hours.... I asked him a question on night at about 11, and after 4 emails till about 1am, transformer was bought and arrived next day....)
Rob

Albert Einstein ― “If you can't explain it to a six year old, you don't understand it yourself.”

#### robertspark

• 596
##### Re: Question on Plasma THC control to users of this facility
« Reply #29 on: November 27, 2016, 08:32:20 AM »
Adrian,  how are you doing the THC  (long term interest of mine.... better thc.... some people chase divots... I seem to chase THCs....)
Rob

Albert Einstein ― “If you can't explain it to a six year old, you don't understand it yourself.”