Hi Piotr
If circuit does not go out of building it is not considered as circuit
with transients. I think you should check other standard like IEC
62151 and IEC 62102 which clasify external circuits.
From my experiences, and I do have quite some, USB is not considered
as external circuit in the sense of clause, where requirements between
external circuit and PE are specified.
Did you also check 62368-2?
Best regards
Bostjan
Poslano iz Outlook za Android <https://aka.ms/AAb9ysg>
------------------------------------------------------------------------
*Od:* Piotr Galka <piotr.ga...@micromade.pl>
*Poslano:* sreda, maj 8, 2024 5:21:33 PM
*Za:* EMC-PSTC@LISTSERV.IEEE.ORG <EMC-PSTC@LISTSERV.IEEE.ORG>
*Zadeva:* Re: [PSES] IEC 62368-1: To understand chapter 5.4.11
Hi Bostjan,
Thanks for your feedback, but...
I am slowly and carefully reading 62368-1 for the first time.
It defines 'external circuit' in 3.3.1.1 as "electrical circuit that is
external to the equipment and is not mains".
I assumed one device = one equipment so I thought laptop is an
equipment. After your post I checked how equipment is defined in 62368-1
but in 3.3 there is no equipment definition so I don't know what is
equipment.
May be USB device (pendrive) connected without cable to laptop can be
assumed being its part, or even device powered by USB (mouse, keyboard)
can be assumed being its part, but USB can be used to connect other
equipment, I think. Do laser printer being powered separately from mains
connected to laptop is understood as being internal part of equipment?
Laptop is probably manufactured by someone else than laser printer. They
can't assume they manufacture single equipment, I think.
In past I have read about USB being used to connect active wifi antenna
located on the roof (with few hubs to extend connection length). Having
all that in mind it is hard for me to accept that for 62368-1 USB is
equipment internal circuit.
Now.
If we assume laptop with connected to it mouse, external keyboard and
printer is one equipment then going to my field: do the access control
controller with RFID readers connected to it by RS485 is also one
equipment (all powered from one 12V supply, and located in one building)
making RS485 connection being internal equipment circuit?
I don't think so.
And I repeat my main question regarding 5.4.11: Do the access controller
permanently connected to 12V supply that is permanently connected to
mains is permanently connected equipment? I think yes. Even 12V supply
has isolation in it.
If I change understanding of equipment and assume that controller + 12V
supply are one equipment than thinks get easier - such understood
equipment is permanently connected. But is it one equipment if
controller is manufactured by someone other then 12V supply.
Best regards
Piotr Galka
W dniu 2024-05-07 o 19:49, Boštjan Glavič pisze:
> Hi Piotr
>
> USB circuit is internal circuit. There are no transients expected on
USB. Clause 5.4.11 is not applicable for power supply with USB output.
>
> Paired conductor is a telecommunication network that we had in old
times (analogue network, ISDN,...).
>
> I hope this helps. If you need more info, you can contact me.
>
> Best regards,
> Boštjan
>
>
>
> -----Original Message-----
> From: Piotr Galka <piotr.ga...@micromade.pl>
> Sent: Tuesday, May 7, 2024 5:40 PM
> To: EMC-PSTC@LISTSERV.IEEE.ORG
> Subject: [PSES] IEC 62368-1: To understand chapter 5.4.11
>
> CAUTION: This email originated from outside of our organisation. Do
not click links or open attachments unless you recognise the sender
and know the content is safe.
>
>
> Trying to understand 62368-1...
>
> I have got laptop with type A power supply so it looks being not
excluded from 5.4.11 by rules in 5.4.11.1.
> For me USB are external circuits indicated in Table 14, ID numbers 1 and
> 2 (I think USB is 'Paired conductor', but even not it certainly is
'Any other conductors').
> The note in Table 14 about not taking into account transients for
external circuits installed wholly within the same building is only
about transients so I think it doesn't make USB being not indicated in
table.
> USB cable can be used to connect laptop to printer and in printer
USB can be earthed, I think.
> Dos this means that according to first sentence of 5.4.11.2 each USB
port in this laptop should be separated from its other USB ports?
> I don't believe there is such requirement.
>
> My real problem to understand is as follows:
> Typical access controller have several not separated from each other
inputs (several RFID reader inputs, door state control input, tamper
inputs and others).
> I need to understand if the access controller powered from (external to
> it) 12V DC buffered (= having accu in it) supply is permanently
connected equipment or not?
> To disconnect it from 12V supply you need tools, to disconnect 12V
supply from mains you need tools, but 12V supply has isolation in it
so access controller is not electrically connected to mains and
3.3.3.4 says about needing tools to disconnect from mains (if
something is not connected than tools are not needed to make it being
disconnected, I think).
> Being permanently connected equipment is the easiest way for
controller to be excluded from 5.4.11.
> But if it is not permanently connected than its inputs are in the
same situation as laptop USB ports I described first as more common to
everyone.
>
> What I miss or wrongly understand?
>
> Regards
> Piotr Galka
>
> P.S.
> Last month free time I spend browsing about 2800 EMC-PSTC posts
collected by my mail program for few years.
>
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