All, The “heavy locked boxes” came in as way to contain the occasionally catastrophic failures that occur with industrial controls. The huge old NEMA rated switchgear was designed to survive a bolted fault of many thousands of amps, which would shower the surrounding area with sparks if not contained.
New panels are typically fitted with IEC rated components which are much smaller and are not designed to take that kind of abuse. IF the overcorrect protection is done right (Type II), they will survive some but not all of life’s vagaries. They may still fail in a shower of sparks and flames. The heavy steel enclosures are there to contain sparks, flames, and exploding components in the event of a contained arc flash. Doug Nix [email protected] +1 (519) 729-5704 > On 4-Apr-2017, at 12:24, Doug Powell <[email protected]> wrote: > > Just my opinion but the use of heavy locked enclosures (pre-dating DIN Rail) > has been industry practice for many years. I suspect that part of the reason > of enclosure similarity is from the desire to keep costs down by having a > minimum number of different boxes in inventory. In addition, NEMA has quite a > bit to say about design for enclosure strength, ingress, accessibility, etc. > > As for the harnesses I feel DIN Rail is a result of organized wiring layouts, > not a cause, I have worked with systems when everything was connected with > ring lugs and very long terminal blocks. It may not be so obvious on smaller > systems but larger systems are often very configurable and rather complex. > This made it much easier to manufacture harnesses in quantity on plywood > board and nail setups with each conductor is identified and tagged on both > ends. I learned my electronics on radar and countermeasures systems in the US > Navy and we had to have wires harnessed and secured cable in this way. I > even learned to tie the standardized knots to use on harness lacing twine. I > haven't checked in a few years but this may still be a practice in military > equipment and I'm pretty sure in avionics too. In industry, the tywrap has > all but taken over. I suspect many of the MIL STD practices have made their > way into industry because they have been proven to work. > > In the early days of mainframe computers, there were attempts to dress out > wiring in a similar fashion and it was found that the cross-talk between > conductors could actually be detrimental. This was likely one of the > contributing factors to the old "rats nest" and thick blankets of 30 AWG wire > used in wire-wrapped backplanes and main frames. The more or less randomly > routed wires were less likely to cross talk when laid out in quasi-orthogonal > arrangements and when squeezing out every bit of speed was imperative, direct > point to point wiring was just a tad bit faster. Just for fun, try a google > image search for Cray Computer Backplane. It becomes very apparent why > technicians would pull out their hair. > > -Doug > > > Douglas E Powell > Laporte, Colorado USA > [email protected] <mailto:[email protected]> > http://www.linkedin.com/in/dougp01 > <http://www.linkedin.com/in/dougp01> > > > > On Tue, Apr 4, 2017 at 6:54 AM, Kunde, Brian <[email protected] > <mailto:[email protected]>> wrote: > I notice that most industrial factory machinery is designed with a large > metal electronic box with a hinged door and some kind of keyed lock. Inside > the components are DIN mounted and the wiring is all dressed very neatly in > these gray plastic cable runs with snap-on lids. Every wire is labeled with a > small tag. > > > > Why are these machines so similar in design? Even among different > manufacturers, they look similar. Is there a standard or standards that > dictate exactly how this is done? What criteria is used to determine if your > product must follow these construction rules? > > > > Seems strange to me that they are so similar and if required to be that way, > then standards and/or governments are dictating design. Even if it was for > the “greater-good”, I thought that was a no-no. Dictate design, stifle > creativity, invite those who would take advantage for financial gain. > > > > Just curious. I’m most interested in the criteria question, though. > > The Other Brian > > > > LECO Corporation Notice: This communication may contain confidential > information intended for the named recipient(s) only. If you received this by > mistake, please destroy it and notify us of the error. Thank you. > > - > ---------------------------------------------------------------- > 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] <mailto:[email protected]>> > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieee-pses.org/emc-pstc.html > <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/ > <http://product-compliance.oc.ieee.org/> can be used for graphics (in > well-used formats), large files, etc. > > Website: http://www.ieee-pses.org/ <http://www.ieee-pses.org/> > Instructions: http://www.ieee-pses.org/list.html (including how to > unsubscribe) <http://www.ieee-pses.org/list.html> > List rules: http://www.ieee-pses.org/listrules.html > <http://www.ieee-pses.org/listrules.html> > For help, send mail to the list administrators: > Scott Douglas <[email protected] <mailto:[email protected]>> > Mike Cantwell <[email protected] <mailto:[email protected]>> > > For policy questions, send mail to: > Jim Bacher <[email protected] <mailto:[email protected]>> > David Heald <[email protected] <mailto:[email protected]>> > > > > > -- > > Douglas E Powell > > [email protected] <mailto:[email protected]> > http://www.linkedin.com/in/dougp01 <http://www.linkedin.com/in/dougp01> > - > ---------------------------------------------------------------- > 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] <mailto:[email protected]>> > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieee-pses.org/emc-pstc.html > <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/ > <http://product-compliance.oc.ieee.org/> can be used for graphics (in > well-used formats), large files, etc. > > Website: http://www.ieee-pses.org/ <http://www.ieee-pses.org/> > Instructions: http://www.ieee-pses.org/list.html (including how to > unsubscribe) <http://www.ieee-pses.org/list.html> > List rules: http://www.ieee-pses.org/listrules.html > <http://www.ieee-pses.org/listrules.html> > For help, send mail to the list administrators: > Scott Douglas <[email protected] <mailto:[email protected]>> > Mike Cantwell <[email protected] <mailto:[email protected]>> > > For policy questions, send mail to: > Jim Bacher <[email protected] <mailto:[email protected]>> > David Heald <[email protected] <mailto:[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://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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
