# variable current and voltage power supply

#### bootlegengineer

Joined Dec 5, 2016
57
Hi! I've been doing a lot of digging online to find a variable current and voltage power supply that can go from 0-240v and 0-400a with a maximum of 5kw, but cant seem to find anything like that anywhere. Obviously I wont be able to get exactly those specs because of losses due to efficiency, but I would like to get as close to to those specs as I can. Basically, I would like this power supply to be an all purpose one so I can have a way to adjust to any voltage and current rating I want within the limits of 4800w (which is the amount of power supplied by a 240v 20a line). Pretty much if you were to combine an inverter mig welder with an inverter stick welder, you would get the kind of power supply I'm looking for. I would greatly appreciate the help!

#### MisterBill2

Joined Jan 23, 2018
8,264
Hi! I've been doing a lot of digging online to find a variable current and voltage power supply that can go from 0-240v and 0-400a with a maximum of 5kw, but cant seem to find anything like that anywhere. Obviously I wont be able to get exactly those specs because of losses due to efficiency, but I would like to get as close to to those specs as I can. Basically, I would like this power supply to be an all purpose one so I can have a way to adjust to any voltage and current rating I want within the limits of 4800w (which is the amount of power supplied by a 240v 20a line). Pretty much if you were to combine an inverter mig welder with an inverter stick welder, you would get the kind of power supply I'm looking for. I would greatly appreciate the help!
You are seeking one MONSTER power supply, with amazing capabilities. It is possible to regulate either voltage or current, but not both at the same time.
The good news is that you can buy such a power supply, the bad news is that it will be quite expensive, and it might need a 3-phase power feed.

#### SamR

Joined Mar 19, 2019
3,202
cant seem to find anything like that anywhere
Because no one makes them for sale due to the fact that there is no demand for such a beast. You will have to build it yourself. How much money are you willing to spend doing so? It won't be cheap! You most likely will not find all the parts to do so "off the shelf" and will have to fabricate them yourself or contract them out.

#### crutschow

Joined Mar 14, 2008
26,812
Do you have a real need for that much voltage and power, or is it just something you would like to have?

I hope you have a generous budget for such a beast.

#### MisterBill2

Joined Jan 23, 2018
8,264
Power supplies of this size and larger ARE for sale, presently the sellers are aiming for the EV developers Check the advertising sections of "evaluation Engineering" magazine.

#### Dodgydave

Joined Jun 22, 2012
9,920
What are you wanting to use it for, welding?

#### MisterBill2

Joined Jan 23, 2018
8,264
Certainly it is in the range that would be used for electric vehicle drive system development.

#### bootlegengineer

Joined Dec 5, 2016
57
Thanks everyone for all the insight! Yea I was worried that might be really expensive to buy one if it even existed. In terms of what I would use it for, I want it to be an all purpose bench power supply so I can use it for basically anything from light/medium duty welding to running a small arc furnace to testing amplifiers to powering a rectifier to charge batteries... all that stuff and a lot more. I like to build and invent things in my free time and having a power supply like that would greatly reduce the hassle of having to keep track of various power supplies that all supply different voltages and current.

Are there any circuits out there that can increase/decrease current as voltage decreases/increases as well as allow manual adjustment? Maybe a transformer that has a tap on the secondary coil that moves along the winding? If this exists or is plausible to make, I can use the transformer or circuit to increase/decrease the current/voltage and then hook the output of that into some sort of circuit that can be used to manually regulate current exclusively, as well as handle such a wide range of voltage and current with minimal losses. perhaps the second circuit could be an isolation transformer with a movable secondary winding and open top?

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#### MisterBill2

Joined Jan 23, 2018
8,264
Running a large power supply to power a small load is terribly inefficient, and many loads will not needover ten amps, so a supply with a 400 amp capacity. would be very un-efficient. So really you need multiple supplies.

Joined Jan 15, 2015
5,893
When I wanted high current, 200 plus volt supplies I went to the guys who made them and no, they do not come cheap. I looked at what they had off the shelf and what I could have custom built. One such supplier I used, here in the US, was DEC (Darrah Electric Company) I assume you already have 240 volt 400 Amp plus service available? You do not mention an output control type? Anyway you are not looking at a basic hobby bench supply, matter of fact I doubt you will find a 220 VDC 400 Amp supply on a bench. Floor maybe, on wheels. You do realize under a 200 volt 200 Amp load you will need some large diameter cable don't you?

You need to spec what you actually want. With realistic numbers for your applications. Then add the features you want or need along with control types.

Ron

#### Irving

Joined Jan 30, 2016
1,174
As MisterBill says, multiple supplies are the solution. I have an old but serviceable 4channel bench supply, a GW GPS4303 picked up on eBay for around 100gbp that does 2 X 30v, 3A +5v/3A and 8-15v/1A. Then for testing higher power stuff, motors, charging batteries, etc a pair of ZDX 3kW (0-60v/0-50A) ex-telecom supplies that can be put in series or parallel if necessary.

Edit: forgot to say, before the ZDXes I had 2 ex-server 24v/100A fixed voltage supplies with various homebrewed or eBay'd buck converters as necessary.

Edit2: also my ZDX are modified with Anderson connectors on rear panel as banana plugs melt at >35A!

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#### MisterBill2

Joined Jan 23, 2018
8,264
We have right here, about 5 miles away, a company called "Controlled Power", which custom builds power supplies. I once had them quote a 12 volt 30 amp power supply for a project that my company was doing. They came back with a price of about $1500, which was a bit high, we thought. We finally purchased one from Newark Electronics, physically a much smaller package, for about$175. That was the one that we used in the tester package that we sold to our client, and it worked very well for them for years, until that production line of theirs changed.
BUT "Controlled Power" will be happy to build the supply you asked for, in a large package with heavy-duty castors, and big power cables. Not cheap by any means, though.
A caution, there is another company nearby called "Control Power", not at all the same company. They do hydraulics and testing machines.

#### bootlegengineer

Joined Dec 5, 2016
57
Yea I suppose you guys are right. It probably would be best to just have multiple smaller power supplies or just like a standard 240v 5kva variac and rectifier for most of my testing. Then I could just make a large transformer and rectifier with a bunch of taps for all of my projects that demand higher current at lower voltage.

#### BobTPH

Joined Jun 5, 2013
3,010
What you are asking for is similar to: "I want an all purpose vehicle. It needs to be able to carry the load of semi and have the accelerations of the Tesla Roadster, (and hopefully fit in small parking places.)"

Bob

#### bootlegengineer

Joined Dec 5, 2016
57
Lol yea sounds about right. Its no problem. I can just live with multiple power supplies.

#### MisterBill2

Joined Jan 23, 2018
8,264
Lol yea sounds about right. Its no problem. I can just live with multiple power supplies.
One extra benefit from using smaller supplies for lower power work is that they are physically much easier to deal with and often more efficient for the application.

#### andrewmm

Joined Feb 25, 2011
1,147
Multiple smaller supplies also.
A lower current supply tends to have better regulation than a big one,
Your probably going to want many different volts at once, so you are going to need a few supplies,
Small supplies are much easier to move around the lab /office.

Putting 240 v at 200 A across 12 V device makes for a real bad day ,