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Can the requirements for protection of wound components against mechanical stress in G.5.1.2 be waived if an Insulation System is used according UL 1446?

More specifically you asked: When two winding wires, or one winding wire and another wire, are in contact inside the wound component, crossing each other at an angle between 45 degrees and 90 degrees without mechanical protection, can Annex G.5.1.2 not be required if the transformer has an insulation system (UL 1446)?


In response, transformers used as safeguard providing Basic, Supplementary or Reinforced Insulation are required to comply with G.5 as referenced in 5.5.3 and  Also, per, if the measured temperature exceeds Class 105(A) limits, they are required to have a suitable insulation in accordance with IEC 60085, or UL 1446 (according Annex DVF


Sub-clause G.5.1.2 includes both a prescriptive option and a performance option (endurance test per G.5.2). 


As noted in compliance criteria in G.5.1.3, there are special allowances for wires tested per Annex J. Such wires (sometimes also known as “Triple Insulated Wires”) that meet Annex J are UL certified under the category OBJT2 (Single- and Multi-layer Insulated Winding Wire) - see also the requirements in Annex DVF Annex J that such wires should meet UL 2353.


Insulation Systems that meet IEC 60085 can be found in UL Product iQ under the category ODCA2 (Insulation Systems, Electrical, Certified to IEC Publications), while Insulation Systems according UL 1446 are certified under OBJY2 (Systems, Electrical Insulation).  Such Electrical Insulation System (EIS) certification covers exclusively the evaluation of the chemical compatibility of material used in a system. Electrical testing, such as temperature or overload testing, on the final wound transformer are not included, in addition to there being no construction analysis. These mechanical / electrical requirements need to be based on the individual standard used for the end-product certification, such as UL / IEC 62368-1.


Therefore, the answer to the question is no, use of an UL 1446 System does not waive the mechanical requirements in G.5, neither the prescriptive nor performance option.

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