EN 61558-2-14-2013 pdf download.Safety of transformers, reactors, power supply units and combination thereof -Part 2-14: Particular requirements and tests for variable transformers and power supply units incorporating variable transformers.
— for class I transformers not intended for connection to the mains supply by means of a plug, the Insulation between the Input windings and the body connected to earth shall consist of at least basic insulation rated for the input voltage. The insulation between the output windings and the body connected to earth, shall consist of at least basic insulation (rated for the output voltage):
— for class I transformers intended for connection to the mains supply by means of a plug. the insulation between the Input windings and the body shall consist of at least basic insulation, and the insulation between the output windings and the body shall consist of at least supplementary insulation (both basic and supplementary insulations rated for the working voltage);
— for class II transformers, the insulation between the Input windings and the body shall consist of double or reinforced insulation (rated for the input voltage). The insulation between the output windings and the body shall consist of double or reinforced insulation (rated for the output voltage).
19.1.3.3 For transformers with intermediate conductive parts (e.g. the iron core) not connected to the body and located between the input and output windings the insulation between the input windings and any intermediate conductive parts shall consist of at least basic Insulation, and the insulation between the output windings and any Intermediate conductive parts shall consist of at least supplementary Insulation (both basic and supplementary insulations rated for the working voltage).
NOTE 1 An intermediate conductive part not separated from the input or output windings or the body by at
least insulation is considered to be connected to the relevant part(s),
NOTE 2 Basic insulation and supplementary insulation are interchangeable
In addition, the following applies:
— for class I transformers, the insulation between the input and output windings via the intermediate conductive parts (even if they are connected to earth) shall consist of double or reinforced insulation (rated for the working voltage):
— for class II transformers, the insulation between the input windings and the body, and between the output windings and the body via the intermediate conductive parts shall consist of double or reinforced Insulation (rated for the input and output voltage):
— for transformers different from independent (lPOO), the insulation between the input and output windings via the intermediate conductive parts shall consist of double or reinforced insulation (rated for the working voltage).
NOTE 3 In this clause the possibility to consider the Intermediate conductive part connected to earth and consequently to require basic Insulation in both circuit (primary and secondary) is not allowed for the following reasons:
— the lnt.rm.dIate conductiv, parts are normally the iron core made by laminated plates insulated each other by oxide. It is not assured that all foils are correctly connected to the earth;
— for transformer different from independent it is not assured that in the final applications the iron core will be connected to earth
19.1.3.4 For class I transformers not intended for connection to the mains supply by means of a plug, the insulation between the Input and output windings may consist of basic insulation plus protective screening instead of double or reinforced insulation, provided the following conditions are complied with:
— the insulation between the input winding and the protective screen shall comply with the requirements for basic insulation (rated for the input voltage):
— the insulation between the protective screen and the output winding shall comply with the requirements for basic insulation (rated for the Output voltage):
— the protective screen shall, unless otherwise specified, consist of a metal foil or of a wire wound screen extending at least the full width of the Input winding and shall have no gaps or holes:
— where the protective screen does not cover the entire width of the input winding, additional adhesive tapes or equivalent insulation shall be used to ensure double insulation in that area:
— if the protective screen is made of a foil, the turns shall be insulated from each other. In case of only one turn, it shall have an isolated overlap of at least 3 mm:
— the wire of a wire wound screen and the lead out wire of the protective screen shall have a cross-sectional area at least corresponding to the rated current of the overload device to ensure that if a breakdown of insulation should occur, the overload protective device will open the circuit before the lead-out wire is destroyed;
— the lead-out wire shall be soldered to the protective screen or secured in an equally reliable manner.EN 61558-2-14-2013 pdf download.
EN 61558-2-14-2013 pdf download
PS:Thank you for your support!
