Long post from this weekend's studies.... I have been thinking about power distribution system tradeoffs for large systems where multiple AC/DC power supplies are used. Surveying 5 or 6 suppliers, picking an arbitrary 100W - 200W range for comparison, I see in-rush current specs with a very wide range (14A to 80A) and a bit of variation in the specified voltages. Some like to specify at 200VAC, others at 230VAC -- all are auto-switching universal input, so the datasheet numbers must be scaled to make an equivalent comparison.
Targeting a 50-70% of full load rating for improved reliability seems reasonable from reviewing qualification data, as well as past discussions with two suppliers. That will in some cases increase the number of power supplies in the system based on mounting location, ease of manufacture and cabling for a large physical structure. Voltage drop on the DC output is another parameter that affects power supply location. I'd appreciate feedback about in-rush current limiting hardware at the system level. I've seen power supply specifications with block diagrams that identify in-rush limiting circuitry which I expect are mostly either NTC's or planar surge resistors. At the system level, it looks like three main options: a hybrid surge resistor/bypass relay module (European suppliers(?)), a softstart controller (targets motor applications) and switched outlet PDU's for data center applications. I think the hybrid module is best for a largely capacitive inputs and these modules' datasheets give a capacitive load rating (1500uF up to 10000uF from what I've seen so far). Network access for the smart switched outlet PDU is probably not an option for the system design. There also look to be moderate cost differences by technology type/application. Any good reference material beyond supplier datasheets and application notes? I've done some searching this weekend and have seen one general lighting reference with estimates for rectifier/PFC topologies of being 30-100x of operating current for in-rush, which doesn't mate well with how the circuit breakers are spec'd (10x to 30x for the millisecond range in-rush transient). I've also seen a few data center-oriented papers and quite a few pages/papers for inductive motor in-rush applications which is not what I am considering. Any suppliers of preference worth evaluating for in-rush limiting for a 12-16A operating current application with common AC/DC open/closed frame supplies? Is the 50-70% FL de-rating for improved reliability a common design target? Other design attributes that jump to the forefront for you? Thanks for reading the whole way through and giving it some thought! Cheers, Adam - ---------------------------------------------------------------- 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>
