Mariano Fe de Leon wrote the following: My response is below. > Re: Transformer Construction.. IEC 950 VS. IEC 601-1-1
> The transformer is used in an equipment evaluated per IEC 601-1-1. The > primary concern is > the creepage distance between the primary and secondary > windings > The transformer uses a "multiple (triple) insulated wire" for either primary > or secondary > windings The wire insulation consists of three (3) layers > extruded FEP material, each layer is > 1 mil (0.0254 mm). The wire was tested > by VDE per IEC 950 Annex U and a certificate of > conformity issued by VDE > (certificate includes following information: 400Veff, 1000Vp; > 500kHz; "F"; > 'geprufte Abschnitte - 2.9.4.4. 5.3, Anhang C, Anhang U'). > Clause 2.9.4.4 stipulates the following: > * allows wound components without interleave insulation if the winding > wire is > insulated with polyimide or FEP and complies with annex U. > * three constructional layer of insulation (of polyimide or FEP) satisfy > the criteria for > reinforced insulation. > * two such wires crossing at an angle between 45 and 90 degrees only > require an > insulating sleeving or sheet material to relieve mechanical stress > at the crossover > point. > This clause appear to indicate that the creepage distance requirement (per > table 6) for > reinforced insulation between the primary and secondary > windings does not apply to this > type of construction (using triple > insulated wire for the winding). > Is this a valid assumption?? > Does clause 2.9.4.4 imply that both the primary and secondary windings of the > transformer > must be the triple insulated wire or does clause 2.9.4.4 allow > the use of triple insulated wire > for the primary and an enameled magnet > wire for the secondary (or enameled magnet wire > for the primary winding > and triple insulated wire for the secondary winding)?? Comments > please... > As mentioned above, the transformer will be evaluated per IEC 601-1-1 to > comply with > the creepage distance for reinforced insulation.. If the above > assumptions are valid, I am > interested in receiving comments to determine > if a transformer that complies with the > creepage distance requirements of > IEC 950 be considered in compliance with the creepage > distance > requirements of IEC 601-1-1. > Thanks..... > Mariano Fe de Leon > Electrical Engineer > ArthroCare Corp > e-mail: [email protected] > Ph.: (408) 736-0224, Ext 305 > Fax: (408) 736-0226 Hello Mariano: I am fairly familiar with the IEC 950 standard; Regarding the IEC 950 issues with your transformer, and coming from a transformer manufacturers point of view who is heavily into the Information Technology (IEC 950) market, I agree with Rich, and could not add much more. I recently obtained a copy of the IEC 601-1 standard, and am not too familiar with it yet. I do not, however, believe it is safe to use an IEC 950 transformer in an IEC 601-1 transformer application. The requirements, for instance, for REINFORCED or DOUBLE insulation are not the same in these two standards. For REINFORCED INSULATION, at a working voltage anywhere from 150VAC to 250VAC, IEC 601-1 table V requires a minimum 4.0 kV dielectric test. Table 18 of IEC 950 requires only a 3.0 kV dielectric test. Also, the minimum creepage distance for IEC 601-1 for REINFORCED INSULATION at 250VAC is 8.0mm (IEC 601-1 table XVI), whereas table 6 of IEC 950 requires only 5.0mm. Clearances, IEC 601-1, 5 mm, and IEC 950 table 3, 4.0mm. Also, and this is the most important to the transformer and wire in question, the layered insulation requirements of IEC 601-1 are more stringent. If using two layers of insulation, IEC 601-1 requires a minimum 0.3mm thickness per layer. IEC 950 has no such requirement. With three layers, (clause 57.9.4 e of IEC 601-1) there is no minimum thickness requirement, but the dielectric strength requirement per layer is higher than that in IEC 950. I have a sample of annex U wire (from a different vendor than you speak of), and the 0.3mm minumum thickness is certainly not met! Concerning construction and dielectric requirements of Mains Supply transformers in general (which I assume you are talking about), IEC 601-1 clause 57.9.4 requirements appear (to me) to be more stringent than IEC 950 requirements. Also, see clause 57.9.4 g) of IEC 601-1. Leadout sleeving requirement is more stringent in the 601 standard than in 2.9.4.4 of the 950 standard. Sorry to burst your bubble, but unless the transformer is overdesigned with regard to 950, I do not think it will pass IEC 601-1. hope this helps, Mel Pedersen Midcom, Inc. Homologations Engineer Phone: (605) 882-8535 [email protected] Fax: (605) 886-6752
