Countdown to compliance

Dashboard Log out

How to determine whether a component like cap., inductor, FET and IC is considered a Potential Ignition Source (PIS), and what is accurate definition of single fault condition? What is the implementation schedule of IEC 62368-1: 2018 (Ed. 3)?

More specifically you asked, 1) how to evaluate whether cap, inductor or MOSFET on power rail are PIS or not. 2) What's the accurate definition of single fault? For a cap, can we set its resistor to several ohms under single fault condition? 3) How to evaluate whether an IC can become PIS under single fault condition? 4) IEC 62368-1:2018 Edition 3.0 had been announce, any schedule for this ver. will be available to implement? Before 2020/2/20 to replace 60950 and 60065?


Regarding 1), 62368-1 does not distinguish whether a component is a PIS based on type of component, such as capacitor, inductor or MOSFET.  There are two Potential Ignition Source (PIS) types, Arcing PIS and Resistive PIS. Depending on the level of power involved, the specific types of components mentioned above could be a Resistive PIS.  The second edition of IEC 62368-1 defines a component as being considered a Resistive PIS if located in a PS2 or PS3 circuit, and either dissipates more than 15 W measured after 30 s under normal operation conditions, or under single fault conditions of other components, either has an available power level over 100 W for 30 s if power limiting components are involved, or for other components has an available power of 15 W after 30 s. However, the third edition refines these conditions for Resistive PIS to only consider “dissipation” of power through the component, no longer considering “available power.”


Regarding 2), per its definition in, “single fault condition” means with the condition of equipment under normal operation, a fault is introduced to a single safeguard, component or device.  Annex B.4 provides some typical single fault conditions, such as short-circuit, interruption, or disconnection of semiconductors and passive components accordingly.  Where single fault is considered in defining a Resistive PIS, Annex B.4 also is applicable.  Fault simulation applies to the actual circuit and component construction, and there is no alternative approach via use of other simulated components, such as the utilization of equivalent resistor for a capacitor.  Regarding 3), the dissipation through the IC would have to be monitored during single faults of other components.  Keep in mind, the manufacturer can always select to declare a Resistive PIS, so then detailed measurements do not need to be made.  This is common practice for many manufacturers.


Questions like 1-3 are best discussed directly with UL based on your specific situation, and outside of a public forum like this.  Please feel free to contact for such an engineering consult: .


Regarding 4), for the implementation schedule of IEC 62368-1:2018 (Edition No. 3), this has been discussed previously -  please follow these links for your further reference:  ; . Also, the UL Effective Date information can be located here: .  We also provide updates on this topic periodically in our UL LinkedIn HBSE/62368 Group - .


Back to "You ask, we answer"