Dear EMC-PSTC colleagues; I mentioned off-list to Ed Price that almost all of the UPS from Tripplite are in fact "back up" rather than "uninterruptible"; they perform a switch >from conditioned line power to inverter power in the event of an AC main failure. This means that they may produce unknown phase/voltage transitions at the switch point, and could cause some big trouble if they are driving inductive loads or inductive/capacitive suppressors.
If the inverters have a sufficiently non-sine output waveform, they could experience significant load effects from suppressors or line conditioners. I think they would be OK with "passive" MOV suppressors, but harmonics and spike voltages from inductive loads may cause more current flow than normal in the MOV's. They may also not be FCC EMC approved when the load is plugged in to an extension cord, which might be considered a rather large antenna! Barry Rowland Vancouver BC On Monday, June 2, 2003, at 01:45 PM, Cortland Richmond wrote: > > I don't believe there are any power quality requirements imposed on > inverters except those specified by buyers (in the USA, anyway). You can > still buy square-wave inverters, after all, and the "modified sine wave" > could be called "Chock Fulla Harmonic" power. Harmful interference is a > limitation, but not one I'd expect manufacturers to be eager to fix, > except, perhaps, to refund the purchase price. (Who's fixing the zillion > SP's plugged into our toys?) > > And that warranty opens a whole _barrel_ of worms. Does user equipment > with > an integral surge suppressor void the warranty? The consumer doesn't know > it's there, either. I'd imagine state attorneys general would have things > to say about implied warranty of serviceability, if this came to their > attention in a sufficiently egregious way. Passengers would sure hesitate > to get on a liner whose lifeboats were described so unconfidently. > > As for plugging all equipment directly onto the inverter, that's > unrealistic. I install an inverter in or on the battery compartment, in > accordance with manufacturer recommendations, to minimize DC voltage drop. > The inverter is connected to an AC distribution panel (which includes > surge > suppressors and filters). Then equipment I want to run, analyzer, > receivers, signal generators, whatever., plugs into that. An IEC line cord > won't even _reach_ the battery compartment where the inverter is > installed. > > > And a UPS that generates transients enough to fire suppressors, transients > from which users ARE FORBIDDEN TO PROTECT EQUIPMENT, seems to me one to > avoid. Could be, such warranties will end up costing vendors more than > they'd expected. > > Then too, a good corporate counsel would point to the hundreds of > warranties honored in spite of extension cords and surge suppressors, and > convince a trial judge that state implied warranty, and vendor's existing > warranty performance, had voided those restrictions historically, and > presently. > > Cortland > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: [email protected] > Dave Heald: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > Jim Bacher: [email protected] > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc > This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
