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Are all repetitive signals, which exceed the limits of IEC 62368-1:2014 - Table 8, independent of frequency and wave form, considered ES3?

More specifically you asked: IEC62368-1:2014 - Table 8 shows the limits for repetitive pulses. According to the table, any voltage with a peak value above 70,7V will be classed as an ES3. For a device that generates a signal with short duration high frequency bursts (>200kHz bursts for 280 microseconds, with 250 milliseconds between bursts) into a transducer, the first question is whether table 8 is the only applicable table for this type of signal for classifying the energy source? For this signal, even with high voltages and currents, due to the very low active duty cycle of approximately 0,1% the total amount of energy in the signal is very low and the risk of electrical injury is low as well, but based on the table this signal is an ES3.

 

In response, for ES classification within IEC 62368-1 (all editions), the prospective touch voltage, touch current and related frequencies always need to be taken into account. IEC TC108 has identified that Table 8 of IEC 62368-1:2014 does not adequately address high frequency scenarios; therefore it was removed in IEC 62368-1:2018. The revised sub-clause 5.2.2.5 refers to the limits of table 4 (sub-clause 5.2.2.2) or to the single pulse limits (sub-clause 5.2.2.4), depending on the pulse off-time. Note too, currents are measured according to 5.7, which considers frequency of the signal. This change reflects current practice as it is considered a clarification (rather than a major technical change between the editions).

 

Due to the complexity of your question and sub-clause 5.2, the complete answer to this question will depend on the specific construction of the system and realistically cannot be answered in this general forum.  As there appears to be a specific, detailed construction that needs review / analysis, you are encouraged to contact UL for an in-depth consultation, either via your local account executive or via https://62368-ul-solutions.com/contact-ul.html\.

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