re uninterruptible power supply in article qk inn hp col col hp com cab col hp com chris best writes i m no expert at ups s but you said something that made it sound like you didn t realize something on a typical ups well on ours anyway there is no switchover from ac to dc all the protected equipment is always running from the batteries via an inverter with the usual condition of also having them on charge if the power fails big deal the computers never see it until the batteries start to droop but there s something like car sized batteries in that cabinet so it takes a while if you were gonna run the guts on straight dc instead of an inverter why not do it all the time then there d be no switchover to screw things up and no having to sense the failure fast just keep the dc on charge when the power is on and it ll be there in zero time when you need it actually it s a bit more complicated than that i sounds to me your ups takes in ac rectifies it to dc to charge the batteries and then takes the battery dc and chops it to ac again feeding your equipment this approach is the easiest and cleanest way to switchover from the mains to battery once your power kicks out since as you mentioned nothing will know about what happened down the line another way to do the ups scheme is to use the mains until you lose power and then kick in the battery backup with it s inverter to replace the lost power the problem here is the switchover time and you ve got to resync the ac in no time flat unfortunately most everything is built around the assumption that ac is available so the ups guys have to provide and ac output to be usable ya sorta have to make it work with what there already similar story with our telephone system it was first invented back in the s we re still using the same damn system media as they did back then if i have a phone from back then i can assure you it ll work on today s phone system it costs too much to overhaul everyone to a new system so they make it work with what is out there
