How to generate 25VAC at 500 amps?

[JohnnyP]

I was visiting my favorite anodizer today and he asked how he could get 25 VAC at 500 amps.  He said he has 480VAC coming into the facility.

I asked him what he was trying to do.  He was a little coy, but I assume it has something to do with anodizing.

So, I have no idea what waveshape would work.

I googled and found a transformer rated at 50VA:
http://www.grainger.com/product/SQUARE-D-Trans-Fused-1YUW1

So that works out to 2 amps at 25v?

Probably a bad idea to try running 250 of them in parallel. 

I gave him the address of eevblog, he wrote it in pen on the palm of his hand.  Don't know if he will check in.

I don't have the chops to do this, so ambitious electrical power wizards should contact Jeff at Dunham Metal Processing in Orange, CA.

[langwadt]

I was visiting my favorite anodizer today and he asked how he could get 25 VAC at 500 amps.  He said he has 480VAC coming into the facility.

I asked him what he was trying to do.  He was a little coy, but I assume it has something to do with anodizing.

So, I have no idea what waveshape would work.

I googled and found a transformer rated at 50VA:
http://www.grainger.com/product/SQUARE-D-Trans-Fused-1YUW1

So that works out to 2 amps at 25v?

Probably a bad idea to try running 250 of them in parallel. 

I gave him the address of eevblog, he wrote it in pen on the palm of his hand.  Don't know if he will check in.

I don't have the chops to do this, so ambitious electrical power wizards should contact Jeff at Dunham Metal Processing in Orange, CA.

10 big of the shelf toroids ~1500VA, primaries in parallel, ignore the secondaries instead put a single turn* of a big fat wire through each?
you can probably get transformers made with out the secondary.

*Depending on the volts per turn you'll have to tweak the number of transformers/turn to get 25Vac

[cs.dk]

A couple of large old welding transformers should be able to deliver that amount.

[JohnnyP]

ok, transformers, no triac arrays?


"put a single turn* of a big fat wire through each"

Would that be a separate wire for each toroid, or one wire, taking a turn around each toroid?

Thanks for the ideas.

[mikeselectricstuff]

25VAC will be in the ballpark of a welder of some sort, though  welders are more oriented to current limiting than voltage regulation. probably worth a try as it's an off-the-shelf solution. Maybe rent one.

[TerraHertz]

Photonicinduction has a couple of videos:

youtube. com/watch?v=JhOzsFfG1rc
Building A Monster High Current Transformer

youtube. com/watch?v=uXEPy6Za6cI
50,000 Amp Transformer Completed

Though, I strongly question his numbers.
Also, lugs not crimped, therefore he's not getting anything like he expects.
Not to mention Amps * turns capacity of the core.

But this is something in the direction of what the anodizing guy wants.

Edit: Gosh, it's hard to force the forum software to NOT insert direct video images. Remove spaces in URLs.

[langwadt]

ok, transformers, no triac arrays?


"put a single turn* of a big fat wire through each"

Would that be a separate wire for each toroid, or one wire, taking a turn around each toroid?

Thanks for the ideas.

one wire taking a few turns around each toroid effectively putting all the "secondaries" in series

you'll have to look at the spec for that transformer or measure how many volt per turn to figure out how many
transformers/ turns per transformer to get 25VAC

[Tomorokoshi]

Sounds like an interesting project.

However -

It's an anodizing / plating / processing facility. There are probably a lot of other people there. Various chemicals. Much of which is probably insured.

Sure, one could piece together equipment to do the job. (My vote is for the welder transformers. Arc welder or MIG? Need to research. Note: welders often have a fair amount less than 100% duty cycle.) But would the equipment be safe for operation? Would it be built and installed to all applicable codes? Of course, in no fashion would it be approved by or listed with an agency. Slight problem if there is an insurance claim.

It kind of sounds like your vendor is looking for a $2000 substitute for a $20,000 piece of equipment.

[HighVoltage]

Take a high voltage transformer from a microwave oven,
Remove the secondary high voltage winding completely.
And add a heavy cable and wind yourself a high current, low voltage transformer
It works very well
You just have to play with the quantity of windings to get to 25V

[langwadt]

Take a high voltage transformer from a microwave oven,
Remove the secondary high voltage winding completely.
And add a heavy cable and wind yourself a high current, low voltage transformer
It works very well
You just have to play with the quantity of windings to get to 25V

it's got to be one beefy microwave to get a 25*500 = 12500VA transformer

[KenGaler]

If he's plating I'm surprised he wants AC instead of DC.  I've designed DC supplies for plating but never heard of using AC.  I wonder if he really needs DC but doesn't know it.

[T3sl4co1l]

AFAIK, anodizing is a current limited process, as the voltage rises over time, corresponding to the thickness of the layer.  Hard anodize being the highest (around 100V I think?), and typical protective layers being 20-30V.

He would need a rectifier after that transformer, yes.

A welder rated for continuous duty (or cycles in the many minutes at least) would seem quite reasonable.  In the 10kVA range, you'll be looking at 3 phase, certainly, which is fine for both an industrial grade machine like that, and for an industrial factory that's already got it available.   One plus: if you do it by transformer alone, you can use a six pulse rectifier to get continuous DC -- full wave rectified 3 phase draws a power factor somewhere around 0.8-0.9 (not unreasonable, though still runs afoul of .eu harmonics regs if that's a concern) and gives output ripple around 20% (who needs filter chokes / caps?).

Tim

[TerraHertz]

If he's plating I'm surprised he wants AC instead of DC.  I've designed DC supplies for plating but never heard of using AC.  I wonder if he really needs DC but doesn't know it.

Since he's a professional anodizer, I'd expect he'd know the difference.

I'm curious too. It might be something to do with pre-cleaning surfaces? Or doing some treatment to the chemical solutions maybe?

Or, maybe he has a huge rectifier bank lying around spare. But typically the systems would be three phase transformers and rectifier banks.
Final possibility: he's teasing JohnnyP, or testing to see if he knows anything at all about anodizing.

[rolycat]

A quick Google shows that AC anodising is definitely possible, although not common. Some recent papers and patents suggest AC or combined techniques offer some advantages over purely DC methods prior to adhesive bonding.

Maybe the OP's friend has some such scheme in mind?

[OldNeurons]

Probably DC instead of AC if it is for anodisation.
I know this company located in Germany.
http://www.plating.de/en/home.html
I have been using their products for the development of automated plating systems working 24/24.
Very compact and reliable.
They are also flexible, and can build a power supply according your exact requirements.
I know also a sweedish company doing the same. They are more expensive. I can't recall their name right now.

[rolycat]

Probably DC instead of AC if it is for anodisation.
I know this company located in Germany.
http://www.plating.de/en/home.html
I have been using their products for the development of automated plating systems working 24/24.
Very compact and reliable.
They are also flexible, and can build a power supply according your exact requirements.
I know also a sweedish company doing the same. They are more expensive. I can't recall their name right now.

As it happens, the company you mention demonstrates that AC can indeed be used when anodising.

From the relevant page of their website:

pe ANODIZING COLOUR: pulse power supplies pe87 DW COLOUR POWER PULSE series for the aluminium colouring process AC or DC/AC method

[OldNeurons]

Probably DC instead of AC if it is for anodisation.
I know this company located in Germany.
http://www.plating.de/en/home.html
I have been using their products for the development of automated plating systems working 24/24.
Very compact and reliable.
They are also flexible, and can build a power supply according your exact requirements.
I know also a sweedish company doing the same. They are more expensive. I can't recall their name right now.

As it happens, the company you mention demonstrates that AC can indeed be used when anodising.

From the relevant page of their website:

pe ANODIZING COLOUR: pulse power supplies pe87 DW COLOUR POWER PULSE series for the aluminium colouring process AC or DC/AC method

With a need for 500 Amps, in a production environment, I would leave the 'old style' systems on the side. It would need huge transformer, huge rectifiers, etc ...
Go for a modern solution !!! The power supplies from Plating Electronics that I have been using, weighed 12kg, not bigger that my HI-FI amplifier, and deliver 250A over 18 Volts.
All that for a price which is certainly less than an 'old style' system (copper is more and more expensive).

[eneuro]

As it happens, the company you mention demonstrates that AC can indeed be used when anodising.

That is interesting, but never tried AC for anodizing, while quite bulky trafo I've used has synchronized rectifier for anodyzing.

Anyway, there is some equipment available-used their hints for anodizing and they know what are talking about.

http://www.anodizeusa.com/anodizing-systems-hard-coat.php

The power supply is a DC rectifier. The aluminum part being anodized is made the anode (or positive pole) in the system. The most efficient cathodes (or negative pole) are 6063t6 aluminum.

BTW: PC motherboard teardown close to 12V CPU power stages can be source of nice synchronized rectifier drivers - three in the case of ASUS motherboard 

[SArepairman]

What about creating +-12V rails with PWM then using driver? a bit more modern then massive inductors

12500 watts is alot though

[Richard Crowley]

Any way you slice it, 12.5 KVA is orders of magnitude beyond the scope of DIY for amateurs. 
A 12.5 KVA transformer is the size and weight of a large truck or earthmover engine.

[SArepairman]

Any way you slice it, 12.5 KVA is orders of magnitude beyond the scope of DIY for amateurs. 
A 12.5 KVA transformer is the size and weight of a large truck or earthmover engine.

idk though, people made 30kVA home made induction forges that use IGBT. Possible to do this entirely solid state with no coupling magnetics. apart from the final impedance matcher

[Richard Crowley]

idk though, people made 30kVA home made induction forges that use IGBT. Possible to do this entirely solid state with no coupling magnetics. apart from the final impedance matcher

Sure, there are clever solutions for certain applications.  But we don't know enough about the requirements here to assume that any of those novel work-arounds would work here.

[eneuro]

That is interesting what kind of anodizing they want to do with this thing, while when we assume 30 ASF for type III anodizing, than 500A could do ~1.5m2 (square meter) anodizing.

When we put additionaly this recomendation into account:
http://www.anodizeusa.com/aluminum-cathodes.php

Code: [Select]

In addition the ratio of 3 sq feet of anode to 1 sq foot of cathode gave the most consistent anodizing.this would mean that cathode for 500A current could be ~0.5m2.
Is it possible with 1.5m2 anode (anodized part area) and 0.5m2 cathode @ 25VAC only get 500A current between those plates in sulfuric acid bath containing 180-200 grams per Liter of acid? 

NOTE: I assumed type III anodizing in those estimations based on linked data.

[technix]

What I can think of is a huge multi-phase non-isolated switch-mode power supply that draws 20A from the mains...

[Richard Crowley]

What I can think of is a huge multi-phase non-isolated switch-mode power supply that draws 20A from the mains...

12.5 KVA is 31.25 A @ 400V assuming 100% efficiency.