Could you explain more details about Annex K.7.1? Especially for the first 4 paragraph? In actual practice, the interlock switch used in mains circuits hardly have 3mm contact gap. what should i do for this case?
Please note the requirements in K.7.1 have been rewritten in IEC 62368-1 Ed. 3 to try to eliminate some confusion in IEC 62368-1 Ed. 2 and to add more clarity.
As now stated in IEC 62368-1 Ed. 3, the requirements in K.7.1 are intended to address separation distance for contact gaps and interlock circuit elements. The requirements were modified to identify the scenario being addressed which is based on what the interlock is switching, if isolated from mains and the kind of hazard(s) involved, such as life threatening or not. As an alternative to the separation distances, the standard allows for an electric strength test in accordance with 126.96.36.199 for basic or reinforced insulation as applicable. If you have not done so already, we encourage to get a copy of IEC 62368-1 Ed. 3 and read through the requirements as they should, hopefully, be clearer.