Greetings. This is my first post here. I do both EMC testing and product safety, but primarily product safety testing and filings through Underwriter's Laboratories acting as both reviewer and submitter [Technical Administrator] in a two-person safety department.
Reason I present here before you is a bit of a problem I am having with UL concerning an obscure requirement. I am wondering if UL is singling me out over an issue that has to do with the Australian/New Zealand specification for "DC Component from AC Equipment". Specifically this is AS/NZS 3260:1993 appendix 3 (pp 366-67) or IEC 60950 appendix 3. I have an AC powered ITE product that uses two switch mode power supplies output connected in current sharing redundancy with AC input full wave rectification i.e. 'balanced input' design that I have certificates for but in which do not specify compliance with the appendix 3 criteria. Lab tests show these to comply with the 5ma limit for DC neutral leakage but readings are extremely fluctuating and difficult to pin down, but compared to other power supplies that do have certification, reads within limits. The problem is I supply UL with schematics that prove the supply has AC input full wave rectification (balanced input according to the spec and therefore exempt from testing) yet they are demanding test data. Up to that point, I was using a Voltech PM3000A power analyzer for all consumption related measurements including DC component (harmonic zero). When I submitted test measurement data, UL rejected it claiming (correctly) that the meter used had insufficient specs to perform the measurement according to the appendix 3 spec for test equipment. (Voltech had no idea what the PM3000A's series rejection ratio was until I inquired and had them perform cal lab tests to determine the figure -which was dismal at best) Since then, I have acquired a Fluke 8842A DMM (with 85dB NMRR) and attempted measurements but these readings are so wildly fluctuating that I would have to tally and average the data manually (or through GPIB) -which would destroy the accuracy of the measurements taken by a 5.5 digit meter!! Incidentally, the difference in accuracy (or believable numbers) between the Fluke and Voltech is nearly the same. I favor the Voltech with its 'data dump' feature straight to printed copy -very handy. Ok, so now I've got more questions than UL Northbrook or Melville can answer...I ask them how to accurately take measurements of a fluctuating phenomenon and they answer me with something to the effect that their QAS department is negotiating with Australia's counterpart in efforts to gain better understanding. Meanwhile, I've got a product that has been waiting since December '98 to gain full CB for the AS/NZS market. In contrast, I have taken measurements using both Voltech and Fluke meters of all our products and found one product that seems to fail the measurement but has certified compliance to appendix 3 through a New Zealand NRTL. When I asked the failing product's power supply vendor what test instrument they used to submit data they reported 'Voltech PM3000A' so I know they are not being honest. When I talk with the lab in New Zealand they claim 'balanced input' design and therefore no test needed, which UL has accepted. Is anybody else having a ride with UL like this? -I'm dipped in hogwash here... how 'dat for openers? Kyle Ehler kyle.eh...@lsil.com <mailto:kyle.eh...@lsil.com> Assistant Design Engineer LSI Logic Storage Systems Division 3718 N. Rock Road U.S.A. Wichita, Kansas 67226 Ph. 316 636 8657 Fax 316 636 8889 Fax 316 636 8315 --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
