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Huge array of paralleled SMPS's...mitigating the inevitable circulating currents?

Flyback

Well-Known Member
Hi

We are doing a 12kW power supply by paralleling over 40 DCDC modules. This question is not specifically about the modules. It is rather about the nature of “circulating currents” in such large systems, and how they can be mitigated.

The power supply will be made of ten “blocks” in parallel. The blocks are shown in the attached.

Obviously in such a physically large system, there will be some distance between the DCDC modules at either end of the array. Therefore inevitably, we will have large area ground current loops. This is practically unavoidable.

As you know, a current loop, (especially one enclosing such a large area) is unfortunately a nice “receiving antenna” for noise. So we will end up with large amounts of noise getting coupled into our circuit, and it is highly likely that the power modules will be swamped with noise and will malfunction.

Do you agree with us that our best way to mitigate this noise will be to place “ferrite beads” in all of the current loops, such that any circulating current in any loop….will “see” at least one of the ferrite beads? Also, a common mode choke right at the output of each module.

I am certain we won’t be able to get help from the DCDC module vendor since….
1…Our sales volumes are obviously low
2….We are too insignificant an organisation.
 

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Flyback

Well-Known Member
Thanks, thats impressive given that the NDR-480 has no in-built facility for paralleling.
Unfortunately we wont be able to use it as our input is 540-700vdc.
It has to be HV DC to keep the current down.
 

gophert

Well-Known Member
Most Helpful Member
Make sure the inductors on your SMPS's are physically separated to avoid magnetic coupling and noise in your circuit.
 

Flyback

Well-Known Member
Thanks, the inductors with switching nodes connected to them, are inside the DCDC module, and we dont have access to them....but it makes me wonder f we should make a metal cage shield for the module?..and ground the shield.
 

gophert

Well-Known Member
Most Helpful Member
Thanks, the inductors with switching nodes connected to them, are inside the DCDC module, and we dont have access to them....but it makes me wonder f we should make a metal cage shield for the module?..and ground the shield.
it depends, where is the incoming nose coming from? What frequency?

conversely, do you have any concerns with EMI emitted from your power supply (through the air or back up the power lines)?
 

Flyback

Well-Known Member
yes Mu metal is best....cheap alu shields only shield against the E field...but i suppose even thats better than nothing.
 

Flyback

Well-Known Member
Please find block diagrams of two 3.7kW power supplies. One is isolated. One is not. They are otherwise the same.
Which one is more likely to suffer from noise issues which may stop the power supply from operating properly.? (supplying the load)
(I am not so interested in which one would be more likely to fail EMC regulations.)

DCM3623T50M53C2T00 DCDC module datasheet:


BCM4414BG0F4440 DCDC module datasheet:
 

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