"Engineers" doing any sort of direct public work in the U.S. must be licensed or working under a (licensed) PE (in which case they are not an engineer in the eyes of the law) regardless of the discipline. This applies to private consulting firms doing public work or within government agencies. The same "industrial exception" exists in the US and this does carry through to products for sale.
-Dave -----Original Message----- From: Mr. Doug Nix C.E.T. [mailto:d...@ieee.org] Sent: Sunday, March 29, 2015 11:40 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] NEC vs CEC for Transformer Protection John, I can’t disagree with any of your statements, only say that this is what is commonly done in practice. Many machine builders have people doing design work who have only minimal qualifications - 2 yr technician diplomas, or people that have “learned by doing”. It depends on the company involved. This is also frequently true of US machine builders. These shops are often very small and have no engineers on staff. You may not be aware of this, but in the US, there is no requirement that people doing engineering work be licensed, with a few specific exceptions in the civil engineering realm. In Canada, it depends on the Province or Territory. In Ontario, where I practice, the Engineer’s Act contains a clause commonly called the “industrial exception” that is supposed to provide an out to employers who have non-licenced technical people doing work that is considered to be “engineering” under the act. The activities are supposed to be limited to work on the employer’s manufacturing equipment, not product for sale, but in practice no distinction is made. Unfortunately, the other side of this is that the definition of Professional Engineering is so broad that you might be challenged for making your own lunch under the act. It’s a mess, IMO. Anyway, many of the machine electrical designers that I’ve dealt with over the years have never seen a time-current curve, and wouldn’t know how to use one, even if you showed it to them. Ohm’s law? well maybe… Doug > On 29-Mar-15, at 08:58, John Woodgate <j...@jmwa.demon.co.uk> wrote: > > In message <9dd08e56-75ed-4ae5-a80a-26a08324b...@ieee.org>, dated Sun, 29 Mar > 2015, Mr. Doug Nix C.E.T. <d...@ieee.org> writes: > >> Typically, designers in Canada use two general rules for guidance in >> protecting transformers, with little actual calculation of inrush currents >> considered: >> >> 1) If no secondary OCD is provided, then the primary OCD will be selected at >> 125% of rated full load current, if inrush proves a problem, then a device >> with slower opening characteristics will be selected. > > It might need to be too slow to be available. > >> 2) If the secondary is protected at 125% of rated, then the primary OCD may >> be selected at 300% or less of of rated. > > That's a sensible solution. Presumably, the Canadian reg. is encouraging that > solution. >> >> These guiding rules generally allow for inrush and provide some degree of >> protection for the transformer. They also meet the CEC requirements. For >> most industrial controls applications, you will not find designers going any >> deeper than this. I have yet to see a machine builder spend any time on >> temperature rise tests or on detailed inrush calculations. > > OK, but supply voltage/winding resistance is hardly difficult. > >> This does not detract from the need to do the testing and come up with a >> more correctly selected value, but rather speaks to the lack of adequate >> time allowed for design, and the fact that very few degreed electrical >> engineers are employed as equipment designers in Canada, so the level of >> engineering expertise involved in the design is lower than what one might >> expect. > > One hopes that they know Ohm's Law, but realise that one may be disappointed. > > -- > OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk > When I turn my back on the sun, it's to look for a rainbow John > Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK > > - > ---------------------------------------------------------------- > 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>
