I need 200 amps, 30 volts and a way to manage its delivery.

Thread Starter

Mobius1NI

Joined Dec 2, 2016
21
I'm absolutely rubbish with electronics. I know what I want, but don't know how to go about getting it
in the most cost efficient way possible. I need a power supply capable of outputting 200 amps and 30 volts
which needs to run to a series of graphite electrodes the goal of which is to create a chain of arcs so for
instance if the PSU was wired to 10 electrodes then what I would expect to see would be 5 arc's across
5 pairs of electrodes.

I also need a way to manage the power so that these arcs only occur once every 2 or 3 seconds because
it needs to run all day long and so don't want anything burning out.

Can anyone give me an idea what type of power supply I should be looking it?

Thanks
Noel
 

Hymie

Joined Mar 30, 2018
877
Be prepared to pay mega-bucks for such a supply – two of these might suffice as the power source (if they can operate in parallel).

https://www.ebay.co.uk/itm/Keysight...651960?hash=item23a906d278:g:qVsAAOSwJbpbiAhP

But then you will need a control circuit to switch as required – although they appear to have GPIB/LAN/USB control options.

As an alternative to the above, buy 20 of these and wire them in parallel.

https://www.ebay.co.uk/itm/DC-5V-12...hash=item2ab0e12b66:m:mOWu9uFI5789FX7309sLe9w

Although rated at 36V, they include a trimmer pot to adjust the output +/- a few volts.
You would need to check that they can be configured in parallel and then think about how you will control the 30V @ 200A.

It would help if you were to specify the purpose of the arcs.
 
Last edited:

ebp

Joined Feb 8, 2018
2,332
It is going to be virtually impossible to strike arcs at 30 volts unless the electrodes are placed in contact then drawn apart or a mechanism to produce a very much higher voltage is added. To start an arc through air you will need something on the order of 3 kilovolts per millimetre of gap.
 

Thread Starter

Mobius1NI

Joined Dec 2, 2016
21
Thanks for the reply.

I like the idea of that actually, daisy chaining power supplies together because it
gives me a degree of fault protection in the sense that if one power supply blows
then I still have the 19 others running albeit at a slightly reduced output.

But....

What does concern me is the problem of troubleshooting such a fault in case
one supply knocks out the entire chain because at the end of the day, I am not a qualified
electrician, but if it was a simple matter of probing each supply with a portable volt meter
until I figured out which supply wasnt working any longer then then I think maybe even I could
cope with that.

Can anyone confirm if such power supply's can in fact be wired in parallel?

Is there any type of device I could insert into this circuit that would only open
the circuit for enough time for a single set of arcs to occur every 2 seconds rather than
having the arc as a constant? It sounds like the sort of thing a computer chip would have
to manage to me but not sure.
 

Hymie

Joined Mar 30, 2018
877
If you were to wire 20 supplies in parallel, you will almost certainly need to sequence the mains input to the supplies, otherwise the inrush current is likely to trip a protective device.

I don’t see why the supplies could not be configured in parallel, especially if each output is passed through a diode (admittedly it would be need rating to 10A).

Rather than buying twenty, could you buy five and experiment with 50A?

By using 20 supplies, you could use 10 relays, each switching the output of 2 supplies with a contact rating of 20A – rather than one contactor rated at 200A.

The 10 relays could then be driven by a simple 555 timer circuit (with the addition of a transistor at the output) switching as required.
 

jpanhalt

Joined Jan 18, 2008
10,461
Have you considered a welder supply. Miller (big bucks) Dialarc 250 has up to 70 OCV. The "Amico" (ebay) offers 28 OCV and 200A at 60% duty cycle for just $269. A used welder may get you what you need at a reasonable cost.
 

Hymie

Joined Mar 30, 2018
877
Given that with 20 supplies could supply 200A continuously – is it possible to reduce the arc current draw with an increase in arc time to achieve the same result; thereby allowing the use of a lower current supply?
 

ebp

Joined Feb 8, 2018
2,332
You can parallel constant-voltage power supplies but ... (copied and slightly edited from my post in another recent thread):

Connecting voltage regulators of any sort, with a very few exceptions, will typically not result in anything close to equal sharing of the load current. The regulator with the highest output voltage, even if by just millivolts, will supply all of the load current until it reaches its current limit and its voltage begins to decline. The second regulator will then start to supply current. If there are many regulators in parallel, they will tend to "come on line" one by one. If the "load regulation" (decrease in output voltage with increase in output current) isn't very good, you may get current sharing below the current limit of the higher-voltage device.

This is not necessarily a big problem provided the regulators do limit current at a level that protects them from damage. It does mean shorter overall lifetime for the system since temperature is a big player in failure rate and the hotter device will fail first. If they shared equally, this would be less of an issue. In some cases the device carrying the higher current will shut down due to over-temperature. This can lead to complete shut-down if the remaining device(s) overheat before the one(s) that shut down cool sufficiently to re-start. Again, as long as the device can tolerate this, no damage should result, but the system may shut down completely while the supplies cool.

There are methods that can enhance sharing, such as using low-value "ballast" resistors in series with the output of each individual regulator, but this degrades overall voltage regulation accuracy and reduces efficiency.
 

WBahn

Joined Mar 31, 2012
26,265
Oh, the goal will be to create these arcs either under deionised water or in a vacuum, forgot to mention that.
Maybe I missed it, but I didn't see where you addressed the issue of how you are planning to strike these arcs every few seconds?

How far apart are the electrodes when the arc is running?

It sounds like you are planning to run the ten electrodes in series with five gaps. How are you going to manage getting all five arcs struck?
 

Thread Starter

Mobius1NI

Joined Dec 2, 2016
21
Well, the idea I have is to have graphite electrodes as pairs within very close proximity to each other with a larger gap
of separation for the next pair in the series and all of the electrodes are probably going to need to be held in place
somehow, perhaps through purpose made holes in a lid or something along those lines.

but I still don't know how I'd go about getting only one arc a second, like I know with a mig welder
it's handled by a trigger the user pulls but in this instance I need user control to be removed in favour
of some other method.
 

-live wire-

Joined Dec 22, 2017
912
30V*200A = 6kW. You would need to connect it to multiple outlets to avoid tripping the breaker. Probably 4 to be safe. This seems impractical.
 

WBahn

Joined Mar 31, 2012
26,265
Well, the idea I have is to have graphite electrodes as pairs within very close proximity to each other with a larger gap
of separation for the next pair in the series and all of the electrodes are probably going to need to be held in place
somehow, perhaps through purpose made holes in a lid or something along those lines.

but I still don't know how I'd go about getting only one arc a second, like I know with a mig welder
it's handled by a trigger the user pulls but in this instance I need user control to be removed in favour
of some other method.
MIG welders do not just strike an arc by pulling a trigger (at least not in the way I think you might be thinking) -- they still have to strike the arc by getting the wire very close to the metal being welded. It's just that this happens as a natural consequence of the trigger starting the wire feed mechanism.

What is the underlying problem you are trying to solve? If this is some kind of art effect there are almost certainly easier alternatives. If it is some scientific experiment the options may be more limited. But if you explain why you are trying to do this, you might be surprised at the wealth of viable alternatives that the breadth and depth of background represented by the members here can spring forth.
 

shortbus

Joined Sep 30, 2009
8,042
MIG welders do not just strike an arc by pulling a trigger (at least not in the way I think you might be thinking) -- they still have to strike the arc by getting the wire very close to the metal being welded. It's just that this happens as a natural consequence of the trigger starting the wire feed mechanism.
That also isn't quite how a Mig welder works either. The spark/light from the ark in the mig process comes from the wire melting/ vaporizing between the welders tip and the work being welded. The continuous feeding of wire in to the weld gap both fills the gap and fuses the joint.
 
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