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Why was the 250VA limit under G.9 removed in IEC 62368-1 Edition 3, and when applying IEC 62368-1 Edition 3, why does it reference IEC 62368-3, when IEC 62368-3 itself refers to IEC 62368-1 Edition 2?

More specifically you asked: IEC 62368-1 2nd edition G9 says current limit source should be <250VA.  But this sentence is removed from IEC 62368-1 Edition 3, but its called in IEC 62368-3. But when we open 62368-3, it points to IEC 62368-1 Edition 2.  Once IEC 62368-1 Edition 3 comes into picture, or supersedes, the previous IEC 62368-1 Edition 2 is obsolete.  So how can IEC 62368-3 be called in IEC 62368-1 Edition 3 and why does 62368-3 refer to IEC 62368-1 Edition 2?


In response, there are a number of statements in the question that require clarification, which also will serve as the answer.


-IEC 62368-1 Edition 2 has a condition of use for IC Current Limiters that an IC current limiter must be supplied by a power source (in the product) that does not exceed 250 VA. This requirement was changed in Edition 3 to a minimum performance test condition, unless the manufacturer specifies a limitation on the type of circuit the IC Current Limiter is to be used in if less than 250 VA.   The Rationale Document, IEC TR 62368-2:2019, provides the reasoning:


“Regarding the 250 VA provision, this provision is intended to mean that the usual test power source has 250 VA capability as long as the IC is designed for installation in a system with a source of 250 VA or larger. If the power source capability is intended to be less than 250 VA, then the manufacturer must specify so, or test in the end product. Testing at 250 VA is intended to include 250 VA or larger sources because the test program is covering relatively small and low-voltage silicon devices – if these devices pass at 250 VA they likely would pass at higher VA too since they are not electro-mechanical. Also, this allows for more practical associated certification test programs.”


-Regarding the 250VA provision for IC Current Limiters, there is no such provision in IEC 62368-3:2017. The only reference to 250 VA is associated with RFT-V circuits (Table 1).


-Regarding the reference to IEC 62368-1:2014 in IEC 62368-3:2017, this was done because IEC 62368-1:2018 was not published yet when IEC 62368-3:2017 was published.  However, everyone agrees it is confusing, and IEC TC 108 has issued a 108/727/INF (Information) document that states that IEC 62368-3:2017 can be used in conjunction with either IEC 62368-1:2014 or IEC 62368-1:2018. This is a reasonable interim conclusion given the close alignment of both IEC 62368-1 editions in structure, definitions and requirements that influence the application of IEC 62368-3.


Going forward, IEC/TC 108 has no plans to update or modify further IEC 62368-3:2017. Instead, TC108 has started two new work items with the purpose to create two new group safety publications (new standard numbers IEC 63315 (covering Cl 5) and IEC 63316 (covering Cl 6)) that will replace IEC 62368-3:2017.

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