Hello. I have a need for a circuit that is a bit off the beaten path.

I need a solid state way to draw a current of 6-12 volts at approximately 1,000 to 1,200 amperes. I have been using a bank of 10 automobile batteries for the chore, but the cycle time and breakdown on these has been pretty much an indication that there has to be a better way to do business. Any ideas?

What will it be used for?

this could be an interesting thread.

We had a transformer that did that for AC rather than DC on a machine we had. You didn't connect the transformer with wire. Large bus bars.

So, you just control the primary.

Do you really need DC? Is this intermittant or continuous?

You could make your own generater but that can breakdown to. Andy

This is used to do electrochemical machining (ECM for the shorthand) on very hard materials. The battery bank handled the kinds of work I needed to do to show the boys in the head-shed that you could sharpen carbide bits with 12 volts and salt water, but I need a more reliable way that doesn't lose its energy when the weather turns cold. I have looked at using a generator, but I figured I could come here and find out if there is a handier way to drop from 220 volts to 12, and then rectify it to direct current. For this to work, I most emphatically need direct current.

I would start looking for large DC power supplies as used in plating applications along these lines. I have used the company linked to but others manufacture them as well. Your best bet would likely be a used or refurbished unit unless you have deep pockets.

Ron

Well since we're off the beaten path:

There is a cheaper DIY way to do it.

High output Truck alternators.....used preferably. Up to around 400A continuous rated I believe.

Go get yourself a used truck/tractor diesel engine add a couple alternators onto it....3 alternators can deliver your 1200A continuous. Sometimes the voltage is 24V, you'd have to verify the 12-14VDC versions.

It might actually be cheaper to go pick up 10 regular 120Amp automobile alternators and rig them to run off a set of pulleys on a custom shaft driven by a decent gas/diesel or CNG motor. Used stuff of course from wrecking yards as it doesn't really matter which 'brand' the alternators are.

I'd setup a series of breakers , 1 for each (isolated) alternator, to drive an electrical panel via the busbars. Tap your main power from the busbars. That way u can 'ramp' your process by adding current under load so to speak.

That way you wont reverse current on any of the alternators as they won't all be at the exact voltage. Always switch the alternators onto a 'loaded' busbar that is running your process.

Tap a rubber hose off the motor's cooling water system and have it run through a metal radiator that is not bothered by your electrolyte, or powder coat or enamel paint the radiator just in case. Place the raditaor in the process tank as a method to 'warm' your process during the winter months.


If you MUST have <12VDC to run your process, simply setup 2 process tanks and drive both in series....7 VDC each would be avg that way from the alternator bank.

As an aside:

There are EDM machines where I work, it occurs to me that converting EDM to ECM shouldn't be all that difficult. Any thoughts on that Arkansas?

Here is another link for power supplies: Dynapower Corporation & Rapid Power Corporation - Rectifiers, Power Supplies, Transformers

ALso, do you have 3 phase available? At higher voltages?

Mosaic said:

As an aside:

There are EDM machines where I work, it occurs to me that converting EDM to ECM shouldn't be all that difficult. Any thoughts on that Arkansas?

Click to expand...

EDM (sinker style) is usually in the 100VDC range for open circuit(not cutting) and working(cutting) voltage of 20 - 50VDC.

My understanding of EDM power supplies where that they worked at a higher voltage as well and used capacitive discharge based drive circuitry not low voltage high current.

Folks, I thank you for your input. Mosaic has probably come up with the solution we'll use, since I have a scrap yard just down the road. The trick will be getting identical alternators, but I think it would be a very interesting DIY project, and one of the bosses owns the scrapyard in question. I'll keep you posted as we progress...

It sounds like you need something about like an industrial spot welder transformer but most of those are 1 volt or less.

I have wound a lot of my own transformers. 12 volts at 1200 amps is 14,400. watts. Look for a 15KW transformer, remove the secondary winding and replace it with the correct wire size and number of turns to get 8.5 volts AC. Then you need a full wave bridge rectifier high amp diodes to turn that into 12 volts 1200 amps.

I finished rewinding a transformer this summer changing it to high amps low voltage on the secondary. I do not have any 100 amp wire and that stuff is hard to hand wind anyway so I wound 7 secondary windings with #14 wire 15 amps per winding all connected in parallel. This gives me the 100 amps that I need.

Hmm...perhaps it might be easier to get a dozen or so junked Microwave ovens and rewind the Transformers. I have done that to make hi current 12V supplies. Takes about an hour to do one transformer as u gotta grind off the spot welds on the core laminations 1st.

A 15KW transformer isn't often junked as it's got a lot of copper $$ in it.

I think you are overlooking the more obvious source of high current transformers and power supplies in general. Welders.

I have picked up older model Miller and Lincoln 600 amp continuous rated welders for under $100 each.

Arkansas said:

This is used to do electrochemical machining (ECM for the shorthand) on very hard materials. The battery bank handled the kinds of work I needed to do to show the boys in the head-shed that you could sharpen carbide bits with 12 volts and salt water, but I need a more reliable way that doesn't lose its energy when the weather turns cold. I have looked at using a generator, but I figured I could come here and find out if there is a handier way to drop from 220 volts to 12, and then rectify it to direct current. For this to work, I most emphatically need direct current.

Click to expand...

If we go back to the beginnings of this thread the original posts involved the use of a battery bank consisting of about 10 each of 12 volt batteries in parallel to get 12 volts with a 1,000 amp or greater current. The original post involves the use of ECM to sharpen machine tools or something along those lines. This, to my simple way of thinking is along the lines of the power required for plating. Thus I suggested power supplies inline with this type of application. Low voltage and adjustable supplies which as can be seen aren't cheap. It becomes one thing to develop a prototype using ten or so batteries costing less than $100 USD each and buying a $12,000 USD power supply.

Now as to a true industrial application the use of power supplies like those used for EDM (Electro Discharge Machining) isn't practical. EDM uses a submerged arc to do its thing. Most PSUs of this nature have a very high open voltage and also use RF start touch to initiate their arc to do their thing. I don't think the high open voltage is desirable in this case.

I don't see buying a pile of big truck alternators as a good solution either as a viable solution. The reason being is if we have 4 or 5 alternators driven by a gasoline, diesel engine or for that matter an electric motor to try and produce 12 volts at over 1,000 Amps we start looking at a few things, starting with the voltage regulation. Aside from that, how do we get them all running at the right RPM and how do we link them? A massive system of pulleys? Belt driven? Personally, and just my thinking (which may suck) doing it this way seems more simple on the surface than it really is. On the bright side assuming really good efficiency you will only need about 25 HP engine at the desired RPM for this to work. Don't forget the governor at the given RPM.

I like the thinking of TCMTECH as to using a welder type power supply assuming the open voltage can be overcome somehow. I just don't see a welding unit, designed for welding applications as a good solution. Though if I wanted to weld point A to point B TCMTECH would be my choice for advise in the forum and well outside the forum. I sort of view him as better than weld engineers I work with.

Power supplies like anything else are chosen for their intended use. In this case I see the use of a plating type (high current) as the overall best solution. Now if that cost is prohibitive then there is a problem.

OK, for this process the use of salt water as an electrolyte works, however ther is no mention of salt concentration? What is the conductivity of the solution? Makes a hell of a difference for the required current.

When doing the trial using batteries how much current was required? How frequently will the process be used?

Just My Take
Ron

What I am thinking is to use the constant voltage power supply's for MIG, (wire feed) welding operations. Most of them have a low end voltage settable to around 12 - 18 volts at full load and don't overshoot when they get unloaded being their whole purpose is to power a near short circuit arc.

Also depending on the welder power supply many CV types can be easily paralleled for much higher current capacity while still keeping a reasonably well regulated output voltage.

The other advantage is that this method is far easier to setup, operate, and will far more efficient than anything else on the operating cost and outright purchase value.

tcmtech said:

What I am thinking is to use the constant voltage power supply's for MIG, (wire feed) welding operations. Most of them have a low end voltage settable to around 12 - 18 volts at full load and don't overshoot when they get unloaded being their whole purpose is to power a near short circuit arc.

Also depending on the welder power supply many CV types can be easily paralleled for much higher current capacity while still keeping a reasonably well regulated output voltage.

The other advantage is that this method is far easier to setup, operate, and will far more efficient than anything else on the operating cost and outright purchase value.

Click to expand...

Ya know tcmtech now that you mention it I once worked on a project for the MK 50 torpedo program where we used a pair of 1,500 amp (as in really big) welding power supplies connected in a parallel configuration to make heat. Well sort of make heat. We had a 1/2" diameter ID 316 SS line running in multiple loops in a large insulated box. Large as in you walked up to it and looked up. Maybe 20 feet wide and a few feet deep. Been years and I forget how many feet of SS tubing went through the thing loop after loop buried in insulation. The inlet was fed by a huge steam generator. Each end was fed by a bus with multiple parallel cables. Big ass cables. When the welders were fired up, that tube glowed cherry red in there and the end result was super heated steam.

Granted off topic but would leave me to reconsider the use of a large welding power supply as a power source.

Ron

Here is the transformer you need.

**broken link removed**