Hi Piotr, Maximum USB cable lengths are quite short, a few meters, and they are not designed to be part of the ‘building or structure’, hence transients are not considered for these ports. If a USB extender or hub is used to extend the USB and this is wired through the building or structure then transients would be the problem of the hub manufacturer and not your product.
There was/is IEC 62368-3: Safety aspects for DC power transfer through communication cables and ports, which is referenced by IEC 62368-1 however this being reworked by TC108 and as far as I can tell few people are using it in it’s present form. When testing your product under 62368-1 the test house will determine the maximum voltage and current the USB (or serial) port can provide, under normal, abnormal and fault conditions, to ensure that there is no hazard. Best regards, Glyn Payne From: Piotr Galka <piotr.ga...@micromade.pl> Sent: Wednesday, May 8, 2024 9:28 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] IEC 62368-1: To understand chapter 5.4.11 You don't often get email from piotr.ga...@micromade.pl<mailto:piotr.ga...@micromade.pl>. Learn why this is important<https://aka.ms/LearnAboutSenderIdentification> Hi Bostjan, I know that if circuit is not going out of building it is considered being without transients. My doubt is mainly because in 5.4.11 says about circuits being external and indicated in table 14 and according to my understanding 3.3.1.1 USB was external and note about transients in table 14 for me didn't make for me USB being not indicated in table. In my RS485 design even it is in one building I assume during storm up to 50V temporary difference between several grounding points and I use 2 steps protection. I know of two such incidents that after lightning struck directly into the building, many systems stopped working, but ours did. I acknowledge that USB is not external circuit. Thanks a lot. I have never bought any standard abroad and as I have written answering to Johns post I see that 62368-2 is not in current Polish Standard Committee offer. Best regards Piotr Galka W dniu 2024-05-08 o 18:45, Boštjan Glavič pisze: 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><mailto:piotr.ga...@micromade.pl> Poslano: sreda, maj 8, 2024 5:21:33 PM Za: EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG> <EMC-PSTC@LISTSERV.IEEE.ORG><mailto: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><mailto:piotr.ga...@micromade.pl> > Sent: Tuesday, May 7, 2024 5:40 PM > To: EMC-PSTC@LISTSERV.IEEE.ORG<mailto: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. > > - > ---------------------------------------------------------------- > This message is from the IEEE Product Safety Engineering Society emc-pstc > discussion list. 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