I am presently faced with a similar concren on a much smaller 50VA switching transformer that I have told the vendor to get construction only recognition (category XORU2).
My decision is based on how the UL Engineer describes the transformer in MY report. If he calls out the mfg P/N and maybe a physical size, then I am satisfied. But if he mentions n/turns, wire size, spacings, etc.etc, then I will ask the vendor for the construction only recognition. So, my thinking all starts with my own UL engineer. rgds, lou Lou Aiken 27109 Palmetto Drive Orange Beach, AL 36561 U.S.A. tel 1-334-981-6786 fax 1-334-981-3054 mobile 1-334-979-4648 ----- Original Message ----- From: Chris Wells To: 'emc-pstc' Sent: Wednesday, November 15, 2000 7:20 PM Subject: UL rec. needed on custom transformer ??? Question - What is the simplest, least expensive, way to define an isolation transformer used in a UL508 (or similar standard) recognized product? The transformer is a custom design made by a magnetics vendor for use in our industrial products. The product is manufactured under a UL coordinated insulation system or recipe. Do I need the manufacture to obtain a UL construction file? I am concerned about managing our UL inspections since I can not prove the construction at our sight. What is the best way to handle the inspection issues? I run into this issue with some of our switch mode power supply isolation transformers. Typically these have a construction file. But I have been told that I don't always need to do this. I am confused! Details - My latest application is a Current Transformer used in power distributions systems. A power main transformer steps down the supply current to 0-5 Amp and then the CT in my product steps this down again to mA range for measurement purposes. These CTs in my product become referenced safety barriers in the UL product file but do not normally have high voltages on the primary. My magnetics vendor says I do not need the construction file but I do not see how I can get a split inspection with UL inspecting the CT at the vendor, with out this. Is there another way? Guidance on this topic would be most appreciated. Thank you Chris Wells Senior Des Eng. [email protected] Cutler-Hammer 412 490 6862
