On 10/02/2015 03:07 AM, Dekatron42 wrote: > Can anyone direct me to a document that says that it is allowed to sell an > electronic apparatus that uses a primary winding as a secondary winding - I > spent a lot of time Googling this and I can't find anything.
I'm truly amazed that anyone would think that this sort of triviality would be written down somewhere. Just as you wouldn't find, for example, an official document saying that one can use a 2n3904 as a very fast avalanche pulse generator. Or any of the millions of other techniques engineers use to accomplish the job. If you pay close attention to the NEC, you'll see that most requirements can be modified or over-ridden by "good engineering judgement". That is, a competent engineer can look at a specific situation, determine that the cook-book requirement doesn't fit and design a solution specific to the situation. Of course, the engineer assumes liability for any subsequent malfunctions, just as an architect does for new building techniques. I can assume with reasonable certainty that you don't know how the agency approval (UL, ETL, etc) works. There's no massive tome on high that is consulted to determine if a given gadget works. If you take your new design for a transformer-based wall-wart to ETL, they will consult their files to see if there is a testing procedure already on record. If so, you pay them about $2500 and they test your gadget against the procedure. If your gadget covers new area, then you pay them something starting at about $10k for them to develop the testing procedure. THEIR engineers use good engineering judgement based on experience when determining the testing procedure. "Is 2500 VDC for 1 minute enough of an interwinding potential or should it be 4500?" Based on their collected body of experience and data, as well as any applicable standards, they'll select an appropriate value. Contrary to popular belief, at least here in the US, a product does NOT have to have agency approval to be marketed and used, except for a few malignant jurisdictions such as NYC. At Fluxeon, we decided at start-up not to waste the money on agency approvals for our portable induction heaters. We lose a sale here and there but all in all, that has turned out to be the correct decision. As Chief Engineer and as a member of the Board, the onus for product safety falls on my shoulders. My qualification requirements are vastly tougher than any agency would require. A prime example is the output transformer. It has about 1200 VAC on the primary and about 60 VAC on the other. It is also the life safety barrier separating line voltage from the user. An agency might require a safety factor of 5 and require a HiPot test of perhaps 6kVDC for a minute. Every transformer is tested at 8kVDC for one minute primary to secondary. The prototypes and random samples pulled from production are tested at 12KV high frequency AC for 12 hours. High frequency AC is a much tougher test than DC because the HF generates dielectric losses and other effects not seen with DC. > I am also > concerned about safety and what an insurance company would have to say if a > fire breaks out and the culprit is the home built equipment which uses a > primary winding as a secondary winding. I don't know where this widely believed fiction originated from but at least in every state I've lived in, homeowner's insurance doesn't look any further than whether arson was involved. When I place burned after a computer monitor caught fire in the night, the adjuster made a copy of the fire marshal’s report, cut me a check for the policy limit, wished me good luck and left. All over with in 30 minutes. John -- John DeArmond Tellico Plains, Occupied TN http://www.fluxeon.com <-- THE source for induction heaters http://www.neon-john.com <-- email from here http://www.johndearmond.com <-- Best damned Blog on the net https://www.etsy.com/shop/BarbraJoanOriginals <-- please visit PGP key: wwwkeys.pgp.net: BCB68D77 -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/560F2381.1020001%40neon-john.com. For more options, visit https://groups.google.com/d/optout.
