Which OP are you referring to? "The chassis and power supply are grounded via the Protective Earth yellow/green wire."
Attitude is Mind over Matter. If you don't Mind, it doesn't Matter... This email has been displayed using 100% recycled electrons and 100% pure virgin photons. --- On Tue, 3/22/11, Brian O'Connell <[email protected]> wrote: > From: Brian O'Connell <[email protected]> > Subject: RE: Line-Neutral orientation with auto-ranging power supplies > To: [email protected] > Date: Tuesday, March 22, 2011, 4:53 PM > Let us be very careful with this. > > The OP did not state if the component power supply was > Class I or Class II > construction. The OP did not say if the chassis was > internally floated or > referenced to the P.E. terminal. > > The component power supply, for Class I construction, is > required to have > the mains input line and neutral terminals marked. > > Brian > > > -----Original Message----- > From: [email protected] > [mailto:[email protected]]On > Behalf Of Ted Eckert > Sent: Tuesday, March 22, 2011 9:40 AM > To: Jayasinghe, Ryan; [email protected] > Subject: RE: Line-Neutral orientation with auto-ranging > power supplies > > Hello Ryan, > > For ITE, you must design the product to be safe even if > line and neutral > are reversed. IEC 60950-1 does not let you depend on > one of the > conductors as being a grounded conductor for safety. > > > In some applications, there are advantages to having a > polarized plug. > The most common example is a light socket. The > threaded portion of the > socket is connected to neutral and the base of the bulb > contacts line. > When somebody is replacing a bulb, they have a much higher > chance of > contacting the threads of either the empty socket or of the > bulb once the > bulb's threads engage the socket. If the threads are > connected to > neutral, and that neutral line is a grounded conductor, > then the risk of > shock is minimized. > > I am speaking of neutral as the grounded conductor in the > terminology of > NFPA 70, the National Electrical Code (NEC). For > safety in the light > socket application, this means that neutral must be > properly derived and > bonded to ground at the electrical panel. It also > assumes that the outlet > is polarized and wired correctly. Finally, it assumes > that the light > fixture's plug is polarized. > > Many regions of the world do not have polarized plugs, so a > harmonized ITE > standard must assume that either conductor could be > live. (For that > matter, in some power systems, both could be live.) > > Ted Eckert > Compliance Engineer > Microsoft Corporation > [email protected] > > The opinions expressed are my own and do not necessarily > reflect those of > my employer. > > From: Jayasinghe, Ryan [mailto:[email protected]] > > Sent: Tuesday, March 22, 2011 10:27 AM > To: [email protected] > Subject: Line-Neutral orientation with auto-ranging power > supplies > > Dear Group, > > I understand that maintaining the L-N orientation is > regarded as 'good > practice' however I cannot find any hard requirement in > UL60950 and would > like to know the source. > > We manufacture several 1U high ITE products in the 20-40W > range which use > several different models of open frame auto-ranging AC > power supplies. > (100-240VAC to 12VDC). > > We use a short two wire cable to connect the input AC from > a small PCB to > the power supply. (Black-Line and White- Neutral). > > The chassis and power supply are grounded via the > Protective Earth > yellow/green wire. > > In some cases the L-N from our AC-PCB does not line up with > L-N pins on > the power supply, and we ask the manufacturer to reverse > their connector. > > This is not a good approach as it leads to a 'custom' part > and other > documentation issues for the manufacture. > > If we were to go in for product safety testing, NRTL, with > the L-N > orientation reversed on what basis would be rejected. Would > we? > > If a power supply is auto-ranging why would the orientation > be important > as L-L will appear on both pins in a 220VAC circuit. > > Most of these power supplies have fuses for both line and > neutral. > > We also have a few power supplies that claim to be > auto-ranging but have > only one fuse, and I am not sure if these would 'qualify' > for a L-N > reverse. > > The other option we have is to provide manufacturing with > two sets of > cables, but that also can lead to other complications, such > as BOMs which > are power-supply-model-specific. > > Your experience and wisdom is greatly appreciated. > > Ryan Jazz Jayasinghe > Compliance Engineer x1198 > > Canoga Perkins > > Direct:(818) 678-3898 > 20600 Prairie Street > Company:(818) > 718-6300 > Chatsworth, CA 91311-6008 > e-mail: [email protected] > www.canoga.com > FAX:(818) > 678-3798 > > > - > ---------------------------------------------------------------- > This message is from the IEEE Product Safety Engineering > Society emc-pstc discussion list. To post a message to the > list, send your e-mail to <[email protected]> > > All emc-pstc postings are archived and searchable on the > web at: > http://product-compliance.oc.ieee.org/ > Graphics (in well-used formats), large files, etc. can be > posted to that URL. > > Website: http://www.ieee-pses.org/ > Instructions: http://listserv.ieee.org/request/user-guide.html > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > Scott Douglas <[email protected]> > Mike Cantwell <[email protected]> > > For policy questions, send mail to: > Jim Bacher: <[email protected]> > David Heald: <[email protected]> > - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
