Dear Robin, I hope you have your UL1950 standard since I will refer you to some important clauses which will help you a lot. The following serves to respond to your questions:
1. Creepage is defined in clause 1.2.10.1 as "the shortest path between two conductive parts, oe between a conductive part and the BOUNDING SURFACE of the equipment, measured along the surface of the insulation". Bounding Surface is defined in clause 1.2.10.3 as "the outer surface of the ELECTRICAL ENCLOSURE, considered as though metal foil were pressed in contact with accessible surfaces of insulating material". Electrical Enclosure is defined as ............ I give up since I can go on and on and on! Also, refer to Annex F which gives some good examples for creepages and clearances. 2) Need more information on how transformer is being used before I can answer the question. What type of circuit do you have in the primary and secondary winding(s) (hazardous primary, hazardous secondary, SELV, ELV). Are these circuits reliably earthed or unearthed? What are the voltages involved between the primary and secondary windings? 3) TIW is a copper magnet wire with three ultra thin layers of insulation. The wires that I came across have been both UL Recognized and TUV Approved and have been investigated to comply with clause 2.9.4.2 and/or 2.9.4.4 of the standard (exemption for 0.4 mm thick insulation requirement for reinforced or supplementary insulation in 2.9.4.1). 4) I can't tell you about costs but I am seeing more and more constructions of switching power supplies using TIW - I can only assume it is cheaper to use in large production runs. The other advantage is that you do not have to use margin tape or other insulating tape. For example, between a hazardous primary winding (copper magnet wire only) and an unearthed SELV winding (TIW) no additional insulation is needed (assuming the TIW was previously investigated for reinforced insulation in clauses 2.9.4.2 and/or 2.9.4.4 of the standard. The other advantage is safety engineers at the various test labs who hate to dissect transformers love looking into transformers with TIW! 5) Quantum shield? Doesn't seem to be TIW. Hope the above helps. > Dear all, > > We have designs for ferrite transformers need to be compliant > to UL1950. However, some concepts still confused me, > > (1) How do UL define the creepage distance? > (2) We use marginal tapes for the primary winding and > the interwinding also. Then do we need to add > marginal tapes for the secondary winding? > (3) What is triple insulated wire? What are the > critical electrical properties for this wire? > (4) If triple insulated wires are used, what is the > advantages? > (5) Phelps Dodge has got a wire called TZQS wires (wire > with quantum shield), is it a triple insulated wires. > > Many thanks > > Robin Chan > > > ______________________________________________________ > Get Your Private, Free Email at http://www.hotmail.com > > --------- > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to [email protected] > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to [email protected], > [email protected], [email protected], or > [email protected] (the list administrators). > PETER S. MERGUERIAN MANAGING DIRECTOR PRODUCT TESTING DIVISION I.T.L. (PRODUCT TESTING) LTD. HACHAROSHET 26, P.O.B. 211 OR YEHUDA 60251, ISRAEL TEL: 972-3-5339022 FAX: 972-3-5339019 E-MAIL: [email protected] Visit our Website: http://www.itl.co.il --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
