Subj : Re: Need testers
To   : Darkytoo
From : Angus Mcleod
Date : Wed Jun 15 2005 11:49 pm

  Re: Re: Need testers
  By: Darkytoo to Tracker1 on Wed Jun 15 2005 19:54:00

 > Just be careful, theres actually two types of power supplies, SPS and UPS.
 > Most of the cheaper ones are actually switching power supplies, they only us
 > the battery when it detects a power outage and it then switches to battery
 > power in some really short length of time, but if power is fine then the
 > battery goes unused.  BUT, they still call it a UPS.  While the higher end
 > UPS's actually run off the batter full time.  These are best if you have
 > power issues as it's all filtered before it hits the actual computer.  I
 > think the best way to tell is if the UPS gets hot, chance is are it's a REAL
 > ups.

I'd be surprised if top-end UPS's ran an inverter full time.  I believe 
they phase-lock a low-power reference oscillator to the mains line, and 
monitor the line.  If they detect a failure, they turn on the inverter to 
track their reference oscillator.  A massive ferrite transformer is the 
primary protection against poor quality power.

Given that a 50 Hz power line presents the equipment with (essentially) 
100 power failures a second, there really isn't anything wrong with this 
technique, so kong as your mains-monitoring is good.  



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