I have had 48V equipment evaluated as SELV and was able to have the hipot test waived all together due to operational insulation compliance to clause 5.4.4 c) by UL.
I have IEC 950 and it defines a secondary circuit in 1.2.8.2 as "A circuit which has no direct connection to primary power and derives its power from a transformer, converter or equivalent isolation device, or from a battery". This certainly sounds like your case to me. Primary voltage is defined as "directly connected to the supply mains". If your UL test engineer is unfamiliar with telecom equipment you may need to go to the team leader. Patty Elliot Qualcomm, Inc. [email protected] Personal opinions, not corporate At 02:06 PM 10/28/97 -0500, Doug McKean wrote: >I'm having a hell of a time with UL. > >A piece of equipment I'm having tested is >powered with -48vdc from the power grid >in a CO. That power grid takes in AC from >the street, steps it down to 48 VDC rectified, >then passes it across the batteries, finally >distributing it out to the racks in the CO. > >That 48 VDC is SELV for there are fuses all >over the place in the CO right up to where >the equipment in the racks plug into it. > >Under UL1950 3rd Edition, Table 18, page 125, >I'm declaring that the 48vdc is secondary and >I asked to have my equipment tested operationally >at 500V. > >I have had 48vdc equip tested at another >lab and approved to UL1950 3rd Edition >under the same claim above. > >UL says no way. It must be tested under >the PRIMARY heading of Table 18 page 125. > >It is important to note here that I WANT >the hi-pot testing to be done. > >Well, now I'm told that if I demand this >to stay as I originally asked, then I only >get UL1950 2nd Edition until the year 2000. > >I don't understand. I've had this done >before without a problem. > >Also, the power supply people, more than >one, find this to be news to them. Most >of the hockey puck DC-DC converters out >there (that I've dealt with) aren't able >to withstand 1414VDC operational. > >Am I alone here? > >Are other mfrs of 48vdc and 24vdc equipment >intended for COs running into the same thing??? > >Regards, Doug > > >
