Electronics > Power/Renewable Energy/EV's

Earthed enclosures and offline SMPS PCBs?

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Faringdon:
Hi,
Do you agree, that when you have an offline SMPS in a metal enclosure, then the SMPS PCB must obviously have y caps to the earthed enclosure.
Do you agree, that the connection of earth, to the metal enclosure, must be from the earth wire that comes in with the mains cable, and that that earth wire, must connect to the metal enclosure, as near as possible to the point where the mains cable comes in through the enclosure?

Alternatively, the earth wire from the mains cable, can connect to the earthed enclosure at a point as near as possible to the mains cable connector on the  offline SMPS PCB.
Would you agree?...and which of the above two places is best?

tggzzz:

--- Quote from: Faringdon on September 06, 2023, 07:29:22 pm ---Hi,
Do you agree, that when you have an offline SMPS in a metal enclosure, then the SMPS PCB must obviously have y caps to the earthed enclosure.
Do you agree, that the connection of earth, to the metal enclosure, must be from the earth wire that comes in with the mains cable, and that that earth wire, must connect to the metal enclosure, as near as possible to the point where the mains cable comes in through the enclosure?

Alternatively, the earth wire from the mains cable, can connect to the earthed enclosure at a point as near as possible to the mains cable connector on the  offline SMPS PCB.
Would you agree?...and which of the above two places is best?

--- End quote ---

One interesting comment on that...
https://www.eevblog.com/forum/chat/keeping-hold-of-electronics-engineers/msg5047744/#msg5047744

And the preceding post offers some context.

floobydust:
What is the product's method of protection against electrocuting people? Is it reinforced or double-insulated, or is the secondary side PE grounded?
You leave out this critical piece of information which also determines spacings you ask about.

The PE connection to the enclosure must be able to trip the branch circuit breaker, compared to a PCB trace or wire fusing- leaving the enclosure hazardous live.
So a 15A current capability and certifiers I have seen inject 15A for an hour and then inspect.
edit: unless the product has fusing on Hot/Line, then I think the current handling for PE gets reduced to clearing that fuse. It depends on the mechanical of the enclosure and power entry.

Faringdon:
Thanks, yes those are great safety points, and of course, the earthing has the important safety aspect.....in this post, from an EMC viewpoint, how would it best be done?

{I know that all will forgive this question, that absolutely none of your industrial secrets are being revealed here....that the entire industry in whatever country you are from, has already been outsourced to (mostly) China........its already gone...the secrets no more. [RANT bit over]}

Gyro:

--- Quote from: Faringdon on September 07, 2023, 05:45:54 am ---...
{I know that all will forgive this question, that absolutely none of your industrial secrets are being revealed here....that the entire industry in whatever country you are from, has already been outsourced to (mostly) China........its already gone...the secrets no more. [RANT bit over]}

--- End quote ---

If only!

It never was an 'industrial secret', just basic EMC and safety consideration.

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