UL 2353 2021 pdf download – Single- and Multi-Layer Insulated Winding Wire.
3.2 BASIC INSULATION – Insulation that provides basic protection against the risk of electric shock. 3.3 CLEARANCE – The shortest distance between two conductive parts measured through air. 3.4 CREEPAGE DISTANCE – The shortest path between two conductive parts measured along the surface of the insulation. 3.5 INSULATING LAYER – A single, concentric thickness of material that is detectable with an optical or mechanical measuring device. Enamel, bond coats, etc. are not considered insulating layers. See 1.2. 3.6 REINFORCED INSULATION – A single insulation that provides protection against risk of electric shock equivalent to double insulation under the conditions specified in the Standard for Information Technology Equipment – Safety – Part 1: General Requirements, UL 60950-1, the Standard for Medical Electrical Equipment, Part 1: General Requirements for Safety, UL 60601-1, or the Standard for Adjustable Speed Electrical Power Drive Systems – Part 5-1 Safety Requirements – Electrical, Thermal and Energy, UL 61800-5-1. Reinforced insulation is not required to be provided in one homogeneous piece. It may consist of several layers that cannot be tested as supplementary or basic insulation. 3.7 ROUTINE TEST – A test to which each individual sample is subjected during or after manufacture to verify that the sample complies with certain criteria. 3.8 SAMPLING TESTS – A test on a number of samples taken at random from a batch of winding wire. 3.9 SEPARABLE LAYERS – A construction that includes layers of insulation that may be separated in a non-destructive manner. 3.10 SUPPLEMENTARY INSULATION – Independent insulation applied in addition to basic insulation in order to reduce the risk of electric shock in the event of a failure of the basic insulation.
5.1.2 Transformer winding wire with extruded or spirally wrapped insulation where the layers cannot be individually tested and only the finished wire can be tested, shall comply with one of the following constructional requirements: a) Basic insulation: one layer extruded, or wrapped; b) Supplementary insulation: two layers extruded or wrapped (one layer wrapped with 50% or greater overlap is considered equivalent to two layers of insulation); c) Reinforced insulation: three layers wrapped or extruded. 5.1.3 All layers of insulation are not required to be made from the same material. 5.1.4 For spirally wrapped insulation that is constructed such that the creepage and clearance distances between layers, as wrapped, are less than those provided in the minimum creepage and clearance distances for Pollution Degree 1, of the Standard for Information Technology Equipment – Safety – Part 1: General Requirements, UL 60950-1, the Standard for Medical Electrical Equipment, Part 1: General Requirements for Safety, UL 60601-1, or the Standard for Adjustable Speed Electrical Power Drive Systems – Part 5-1 Safety Requirements – Electrical, Thermal and Energy, UL 61800-5-1. The path between layers shall be sealed as for a cemented joint, and tested in accordance with the requirements for spacings filled by the insulation compounds as specified in UL 60950-1, UL 60601-1, and UL 61800-5-1. The test voltages for the electric strength tests are to be increased to 1.6 times their normal values. 5.1.5 One layer of material wound for spirally wrapped insulation with more than 50% overlap is considered to constitute two layers. 5.1.6 Solvent based enamel insulation used to coat the conductor is not to be counted as a layer when determining basic, supplementary and reinforced insulation.