How to rectify 400V-AC, 12-13kW input to a 24V-DC split consumer?

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Hade

Joined Aug 29, 2019
5
Hi everyone,

I am working on a personal project that requires me to create a power supply and charging solution at the same time and I am not really sure where to begin. For starters, the input is 400V-AC at 50Hz, about 12-13kW of power minimum. What I'd like to do is first to convert it to 24V DC, then split it seamlessly between a 24V-DC, 11kW consumer and 1-2kW, 24V-DC battery charger that can work at the same time all while trying to minimise the size of the system of course.

While I was doing the research, I was looking how typical chargers and rectifiers work, most of them increase the frequency significantly with transistors (maybe I could use an IGBT?) to reduce the size of transformers and capacitors used for smoothing but all that is for low power applications and hence hardly applicable to my situation. After quite a lot of reading I have no idea where to even start so I came here to ask you gentlemen (and possibly ladies) for advice on how to tackle this problem.

Is it possible to convert all that power to useable DC without making the system too bulky?
How would I even go about splitting those 2 outputs at the same time?
What if the input power varies from time to time (sometimes it's giving 15-16kW because of higher input voltage) but I need to limit it to 12-13kW, would I use some kind of variable resistor to dissipate the power?
 

dendad

Joined Feb 20, 2016
3,602
At those power levels, you will need to get professionally designed equipment.
What used 24VDC at 500+ amps???
I tend to think the whole idea is quite wrong.
Please post actual details of what the system really is, the more details the better.
What is the supply, the load,......
 

Thread Starter

Hade

Joined Aug 29, 2019
5
The idea isn't wrong, it's what is necessary, the idea is to run a couple of motors and charge a battery off a variable power supply.

I would love to go into detail but unfortunately I can't as what I'm trying to design hasn't been done before and honestly, I don't really want to give the idea away, lets just say that the power supply is variable (in a certain range) that will always output more then what is neccesary for the system to run, but it needs to be limited to the load demand on the DC side. There is no specific power supply I can point to.

I guess if I want to feed the motors and the charger with 24V-DC, I should at first convert AC to DC so I don't have to do it twice separately for the motors and chargers, then split it up for every motor and charger.
 

Alec_t

Joined Sep 17, 2013
11,628
Sorry to put a damper on things, but I agree with Dendad. Even professionals would find this project challenging.
It is clear from your post that you do not have experience in building switch-mode power supplies (SMPS). They can be tricky beasts and finicky over such things as circuit layout and inductance values. At the power levels involved, custom components might be needed.
A motor-generator combo might be more practical than a SMPS.
What is your budget for this project?
 

Thread Starter

Hade

Joined Aug 29, 2019
5
I am still a student, so yeah, definately lacking in experience, but I believe I could learn so much from the project. I understand that the custom components WILL be necessary, the whole build is custom actually, as for the budget, that is kind of starting a fire while the bunny is still in the woods.

The first step of the project is complete in a sense that I needed to find out if the power required by the motors and the charger is even available, after a lot of calculations and modeling I found out that it is, in abundance actually. Now the next step is to find out how would I convert it to something useable, I don't even need a specific solution but just an idea how to go about solving the problem.

Maybe i could use a dropping capacitor circuit instead of a step-down transformer with rectifier?
 

dendad

Joined Feb 20, 2016
3,602
I'm sorry to say, it is almost not worth persevering with you if you will not give details.
The project, as you describe it, is quite impracticable. And your refusal to supply real info makes it almost impossible to help you.
Full disclosure would possibly produce advice on how to solve your problem, but until you are prepared to do that, you are just wasting time.
And your last post just shows you need lots of help.
 

Thread Starter

Hade

Joined Aug 29, 2019
5
I don't need anyone to do the specific calculations for me, or make me schematics or anything like that, just information on how would one go about converting voltages in range from 300-450VAC (as i said variable) to a rectified 24VDC on the power levels I have specified. If you were somebody I know in real life, no problem, we can talk, but as it is, I definately don't have a reason to trust strangers on the internet with the whole project so I'm asking about a segment of it so I can put it together myself. I didn't even get to the part of making schematics or calculations for this segment of the project, I'm trying to make a block-scheme and see if it's even feasible.
Cheers
 

Alec_t

Joined Sep 17, 2013
11,628
Maybe i could use a dropping capacitor circuit instead of a step-down transformer with rectifier?
I don't need anyone to do the specific calculations for me
In that case I suggest you do the calculations to see what size capacitor would be needed to pass enough current for a 12kW load. The answer should convince you of the impracticality of that approach.
I didn't even get to the part of making schematics or calculations for this segment of the project, I'm trying to make a block-scheme and see if it's even feasible.
To see if any scheme is feasible , calculations should be your first step.
 

Thread Starter

Hade

Joined Aug 29, 2019
5
In that case I suggest you do the calculations to see what size capacitor would be needed to pass enough current for a 12kW load. The answer should convince you of the impracticality of that approach.
I hear you, I was thinking something along the lines of dropping capacitor cirtcuit for every line after the supply is split for motors and the charger, capacitors like that exist (cca. 2kW, so about 300-350μF), that's why I haven't discarded the idea right away, that would however require me to have seperate bridge rectifier after each circuit instead of one.


To see if any scheme is feasible , calculations should be your first step.
I don't agree with this if we are on the same page about what a block-scheme is, I need it to visualise an idea first, which segments come in first, then from the wider picture I can focus on the segments themselves and test the feasibility of the solution. What I am trying to do is possible no doubt about it, but does it require a 30kg set-up of step down transformers and other components or can it be done in a smaller form factor is the "feasibility" part I am talking about.

So basically:
Step down the voltage
Rectify it
Split it towards a charge controller and speed controllers for DC motors
(or 1st split it up, then use smaller step down circuits with capacitors and rectify it)
Feed it in the loads
Have a feedback loop that would protect the charge controllers and speed controllers from too much power
 

jpanhalt

Joined Jan 18, 2008
10,210
I hear you, I was thinking something along the lines of dropping capacitor cirtcuit for every line after the supply is split for motors and the charger, capacitors like that exist (cca. 2kW, so about 300-350μF), that's why I haven't discarded the idea right away, that would however require me to have seperate bridge rectifier after each circuit instead of one.



I don't agree with this if we are on the same page about what a block-scheme is, I need it to visualise an idea first, which segments come in first, then from the wider picture I can focus on the segments themselves and test the feasibility of the solution. What I am trying to do is possible no doubt about it, but does it require a 30kg set-up of step down transformers and other components or can it be done in a smaller form factor is the "feasibility" part I am talking about.

So basically:
Step down the voltage
Rectify it
Split it towards a charge controller and speed controllers for DC motors
(or 1st split it up, then use smaller step down circuits with capacitors and rectify it)
Feed it in the loads
Have a feedback loop that would protect the charge controllers and speed controllers from too much power
That's a big part of the problem. Input is 300 to 450 VAC. What step down would you use? In either case, you will need to buck or boost something on the order of 500 A for a constant 24 VDC.
 

ScottWang

Joined Aug 23, 2012
6,933
Maybe i could use a dropping capacitor circuit instead of a step-down transformer with rectifier?
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