Begin forwarded message: > From: "LBRT- UPSTECH, LNA" <upst...@liebert.com> > Date: Wed Jun 04, 2003 01:32:31 PM America/Vancouver > To: "'bfr...@direct.ca'" <bfr...@direct.ca> > Subject: Liebert Hardware Case # 63058 > > > Hi Barry, > > First question about the extension cord. An extension cord is considered > a > temporary installation. A power strip is not an extension cord. We have > power strips we offer in our rack systems, and also have MicroPODs which > are > distribution with bypass options. If someone asks us about additional > surge, we suggest it goes before the UPS. Surge strips are less expensive > than the UPS and generally have better surge protection. > > The UPS is tested to UL-1778 standard. This requires some surge > protection, > but not as much as you get from a quality surge strip. This is why the > surge strip would come first. The concern with putting a power strip on > the > output of a UPS is that many outlets are now available. If someone plugs > a > device into the strip that overloads it, then the UPS could shut down. > This > would be like a cleaning crew plugging in a floor cleaner. > > I do not understand the statement, either, by Tripplite about the UPS > output > causing the surge to "short-circuit the UPS" > > There are two basic types of UPS: (1) off-line and (2) on-line. The off > line models can also be line-interactive models with buck-and-boost modes, > but they are in the off-line type. > > (1) The off-line UPS basically lets utility power pass through it (through > filtering and surge protection) and has to switch on the UPS electronics > to > go to battery mode. There is a relay that has to change state to change > to > battery mode. This is a fast transfer time (~6 mSec), but there is the > break. I have not ever experienced a transient due to this transfer. > Since > this type lets utility power pass through, the output voltage and > frequency > will vary as the utility power fluctuates until the UPS goes to battery > mode. > > (2) The on-line UPS goes through a double-conversion process. The > incoming > utility AC power is rectified to DC, then the UPS inverter circuit is > always > generating the output power. Because of this double conversion the output > power is a steady voltage and frequency. When changing to or from battery > mode there is no interruption of output power. > > I hope I have answered your questions, but if you have any more please let > us know. > Thank you, > John Ufferman, Liebert Corporation > Hardware Applications Engineer > upst...@liebert.com > 1-800-222-5877, opt.3, opt.2. > 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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
