In a message dated 10/25/01, Dave Heald writes:
> If you want to ship to Europe, the nominal voltage can be -60Vdc. Here > it gets tricky as charging voltages are typically 72Vdc. Most NRTL's > testing to the new UL60950 will treat DC input voltages at these levels > as TNV-2, which is a lot better for design reasons than treating your > input circuit as a hazardous voltage circuit. > Hello All: Just a followup on Dave's comment above. In Europe (EN 60950), the definition of TNV voltages in clause 2.3.1 allows levels up to 120 VDC. In the USA there is a D2 deviation that severely limits the use of voltages over 60 VDC, but clause 3.6 of UL 60950 explicitly allows centralized DC supplies up to 80 VDC to be classified as TNV-2. Thus, depending on the specifics of the application, the 60 VDC limit in the UL definition of TNV is not a problem in Europe and may not be a problem in the USA either. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. http://www.randolph-telecom.com
