Dear Jerry, Production-Line Tests are not required by UL1950 but is part of the OSHA NRTL regulations.
UL1950 requires a production-line test of minimum 500 Vac or 700 Vdc between CO dc supplies of up to 60 V. The reason is that although SELV, you need proper isolation between the dc input terminals and earthed chassis. If you did not have this minimum isolation, in case of a fault condition, there could be a hazardous condition of high loop currents between the CO battery source and your equipment which may cause fire. This is analogous to the neutral terminal on your mains supply being isolated from earth. If your equipment does not pass this minimum electric strength test, the UL1950 standard allows you to include specialized installation instructions (refer to Annexes of UL1950 - not sure which Annex since I do not have a copy of the standard with me). In this case, you can ask for an exemption from your NRTL. However, please be advised that if you are a manufacturer of an ITE/Telecom product which is rack-mounted with other units, and the rack has its own connection to the CO supply, then the rack equipment manufacturer might have to include these specialized installation instructions which I understand most COs do not like. Best Regards, > Does UL 1950 require that a production line hipot test be performed on > equipment powered by Central Office -48 Vdc? If so, what is the > voltage/duration? > > I can understand a production line test on 120/220 Vac powered equipment > because you're trying to catch insulation breakdown between line and > ground. What hazard would you be preventing if your equipment is powered > by -48 Vdc in a Central Office? Isn't this SELV? > > Thank you in advance for any replies. > > Jerry > > ___________________________________________________________________ > Get the Internet just the way you want it. > Free software, free e-mail, and free Internet access for a month! > Try Juno Web: http://dl.www.juno.com/dynoget/tagj. 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: pe...@itl.co.il Visit our Website: http://www.itl.co.il
