I would like to add that I (my employer) also have used Tania's #1 suggestion with regards to a similar device. Has worked out well over the past years. Responsibility of compliance stays within the manufacturer's facility and not ours!
-----Original Message----- From: Gary McInturff [mailto:[email protected]] Sent: Thursday, November 16, 2000 10:29 AM To: 'Grant, Tania (Tania)'; 'Chris Wells'; 'emc-pstc' Subject: RE: UL rec. needed on custom transformer ??? Just another vote for Tania's plan outlined below. I have used that in the past, and used path 1. Including I changed potential vendors, when the first guy didn't want to work with me. I paid the investigation fee's, and he paid the follow-up just as Tania described. I'm sure the cost went a few quid when I wasn't looking, but the overall cost of continued compliance was still cheaper with him being inspected rather than me trying to pry open transformers and verifying the system every so often. You may even want to make it an unlisted component - in other words it is recognized only in your files. The vendor cannot now start advertising and selling the transformer as recognized to others. You own the information out of the UL investigation. Why is it called an "unlisted" component when its recognized. UL abhors the use of the term listed in their reports in order to avoid confusion with the word as it is used on a complete product? Gary -----Original Message----- From: Grant, Tania (Tania) [mailto:[email protected]] Sent: Wednesday, November 15, 2000 6:23 PM To: 'Chris Wells'; 'emc-pstc' Subject: RE: UL rec. needed on custom transformer ??? Importance: High Chris, Per your description, your Current Transformer is in a safety circuit. The fact that "normally" you do not have high voltages on the primary side does not cut it. (Besides, what is "high" voltage???) You have several choices (in order of what my preference would be, and money being no object!). However, if I misunderstood you, and your transformer is NOT in a safety circuit, then all you need to do is to prove to UL that this is the case;-- it should be obvious from your schematics. 1. Since the transformer manufacturer already is using a UL coordinated/approved insulation system, it would not take much more money for him to submit this particular transformer to UL. Your company probably should pay for the UL submittal costs, but the manufacturer should pay for UL factory inspections. This way, you are off the hook when he changes construction;-- he has to maintain compliance at all costs, and you don't need to know the details as to how he does this. 2. If the manufacturer is very stubborn for some reason, and does not want to do the above, tell him you will submit the transformer, however, you will need complete construction details that he will have to provide you. Since this is a custom design, he should not mind this. Thus, you pay directly to UL for this evaluation. However, you also designate the manufacturing location the address of your vendor, not your own. (This is not the same as split inspection.) Here, you have more of a headache: you pay for UL factory inspections;-- whenever anything is wrong UL writes you letters about it, since you are the listee and applicant. Thus, you know every time your vendor trips up. Be sure to tell him that now you will have this knowledge! 3. You submit this transformer to UL as described in 2 above, but do not designate the vendor as the manufacturing location. Now you have a very big headache. Whenever the vendor changes construction, you don't know anything about this, and then you get a spiffy UL field inspector who demands that you saw the transformer in half so that he can measure the spacings and count the number of windings! (Don't ever fall for this! You need a laboratory special saw to do this correctly.) I would never never choose this last option! Thus, number 1 is your best choice even if your company has to pay up-front costs for the UL evaluation-- after all, it is a custom design! However, you save money and time down the road. I hope I have given you some justifications for your decision. Tania Grant, [email protected] Lucent Technologies, Switching Solutions Group Intelligent Network and Messaging Solutions -----Original Message----- From: Chris Wells [mailto:[email protected]] Sent: Wednesday, November 15, 2000 5:20 PM To: 'emc-pstc' 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] <mailto:[email protected]> Cutler-Hammer 412 490 6862 ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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