Hi Vijay, **reply below: Regards, Scott
"Wani, Vijay (V)" wrote: > Thank you all for your valuable input. i apologize for late reply. i ordered > a copy of EN60950:2000. (thanks, Chris, George and constantin) and now, it > is getting much clearer. however, i have some questions and would appreciate > any comment. > > as per EN60950:2000, 4.7.2.1: > 1. Except where method 2 of 4.7.1 is used exclusively, or as permitted > in 4.7.2.2, the following parts are considered to have a risk of ignition > and, therefore, require a FIRE ENCLOSURE: > - components in PRIMARY CIRCUITS; > > So if i am interpreting Rich and Scott's e-mail right (great explanation), > i do not need FIRE ENCLOSURE, if primary circuit is supplied by a Limited > Power source. For an existing device, how do i know whether the primary > circuit is supplied by a Limited Power source? are cell-phones, PDA's > typically supplied by Limited Power Source? > **Once you receive your EN60950, go to section 2.5 where LPS is discussed. LPS characteristics are broken down into two major types: 1) inherently limited (inherent in the circuit design-e.g. high impedance source), and 2) not inherently limited (requires an overcurrent protection device). Circuits must perform to the limits within tables 2B or 2C to be classified as LPS. > > as per 4.7.3.4 > 2. Inside FIRE ENCLOSURE, materials for components and other parts, > (including MECHANICAL and ELECTRICAL ENCLOSURE located inside FIRE > ENCLOSURS) shall comply with on of the following: > - be of FLAMMABILITY CLASS V-2 OR FLAMMABILITY CLASS HF-2; OR > - pass the flammability test described in clause A.2; or > - meet flammability requirements of a relevant IEC component standard which > includes such requirements. > > Does this mean; if i have an enclosure inside a FIRE ENCLOSURE, than it has > to be V-2 eventhough there are no safety hazards resulting from complete > disapperance of the enclosure? **Yes. In this scenario (assuming it does not serve as an electrical/mechanical enclosure), the key attribute of the "internal" enclosure you mention is not it's function as an enclosure, but it's fuel load. Therefore, once inside the fire enclosure, the internal enclosure is simply another internal "component" and must meet the flame rating for internal components or otherwise comply with the exemptions outlined in the standard. > > > thank you. > > vijay wani > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@attbi.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > http://ieeepstc.mindcruiser.com/ > Click on "browse" and then "emc-pstc mailing list" ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
