I don't believe the justification for that power distribution is safety-related. After all, most aircraft are made of aluminum, and they don't route power that way. The reason for what the Navy does is, per my understanding, related to reliability during battle, i.e., surviving battle damage. Electrical power is not referenced to ship structure, therefore any single phase can get shorted to structure without disruption to electrical power distribution.
It would be interesting to know how electrical power is routed in the merchant marine fleet where battle damage isn't expected. Ken Javor Phone: (256) 650-5261 > From: Doug Powell <doug...@gmail.com> > Reply-To: Doug Powell <doug...@gmail.com> > Date: Fri, 14 Nov 2014 09:50:35 -0700 > To: <EMC-PSTC@LISTSERV.IEEE.ORG> > Subject: Re: [PSES] Safer: 50/60 Hz or 400 Hz? > > All, > > Regardless of reduced severity, we should never assume a particular frequency > is "safer". All of these voltages are unsafe. It's simply that as you go to > higher frequencies, "skin" effect begins to play a role. Eventually you get > into the realm of RF burns. IEC 61010-1 mentions this in Annex A, circuit A.3. > > > I have personally experienced a shock on 400 Hz, 440 Vac power in the US Navy. > If 50 Hz or 60 Hz is a buzz, 400 Hz is like a scream. I attribute my > survival at the time to working in the tropics and a film of sweat over my > entire body. I believe my skin impedance was much lower over the surface. > > The Navy did another interesting thing. Since most ships are a made of steel, > it means you are standing on conductive floors (decks) at all times. Where I > was stationed the normal shipboard power for 120 VAC was configured as split > phase, L1, L2, earth and no neutral. It was thought that a shock of 60 Volts > to ground was more survivable. > > Thanks, - doug > > Douglas Powell > http://www.linkedin.com/in/dougp01 > Original Message > From: Nick Wright > Sent: Friday, November 14, 2014 9:07 AM > To: EMC-PSTC@LISTSERV.IEEE.ORG > Reply To: Nick Wright > Subject: Re: [PSES] Safer: 50/60 Hz or 400 Hz? > > Hi Dave, > > Medical standard EN60601-1 specifies risk associated with supply frequencies > up to 1MHz by effectively de-rating allowable leakage currents. Higher > frequencies are statistically less dangerous in terms of causing fibrillation. > 50Hz and 60 Hz are about the same, 400Hz is about 0.75 less dangerous than > 50/60Hz for a given current. > > Nick Wright > > ______________________________________________________________________ > This email has been scanned by the Symantec Email Security.cloud service. > For more information please visit http://www.symanteccloud.com > ______________________________________________________________________ > > - > ---------------------------------------------------------------- > 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 > <emc-p...@ieee.org> > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieee-pses.org/emc-pstc.html > > Attachments are not permitted but the IEEE PSES Online Communities site at > http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used > formats), large files, etc. > > Website: http://www.ieee-pses.org/ > Instructions: http://www.ieee-pses.org/list.html (including how to > unsubscribe) > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > Scott Douglas <sdoug...@ieee.org> > Mike Cantwell <mcantw...@ieee.org> > > For policy questions, send mail to: > Jim Bacher: <j.bac...@ieee.org> > David Heald: <dhe...@gmail.com> > > - > ---------------------------------------------------------------- > 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 > <emc-p...@ieee.org> > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieee-pses.org/emc-pstc.html > > Attachments are not permitted but the IEEE PSES Online Communities site at > http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used > formats), large files, etc. > > Website: http://www.ieee-pses.org/ > Instructions: http://www.ieee-pses.org/list.html (including how to > unsubscribe) > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > Scott Douglas <sdoug...@ieee.org> > Mike Cantwell <mcantw...@ieee.org> > > For policy questions, send mail to: > Jim Bacher: <j.bac...@ieee.org> > David Heald: <dhe...@gmail.com> - ---------------------------------------------------------------- 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 <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
