The use of TIW (Triple-Insulated-Wire) in the construction of SMPS (Switch-Mode-Power Supply) transformers is something very common nowadays since it reduces the size of the component, increases efficiency, and helps to reduce the consumption of tape insulation.
It also makes the design of construction much easier from the perspective of clearances and creepage distances. The most used standards on the component level for TIW were IEC 60950-1 Annex U and IEC 60601 Annex L in the past and IEC 62368-1 Annex J lately.
While these standards remain dominant, for applications of SMPS used in household appliances covered by IEC 60335 series of standards and general purpose SMPS power supplies covered by IEC 61558 series, it is required to prove compliance according to Annex K of IEC 61558-1:2017 or IEC 61558-2-16:2009 +A1:2013 standard.
Although tests performed according to Annex K are identical if compared to other standards, the main difference is in test voltages applied during tests which are much higher in Annex K.
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