[mythtv-users] Power outages and UPSs

f-myth-users at media.mit.edu f-myth-users at media.mit.edu
Mon Jul 30 23:32:01 UTC 2007


    Date: Mon, 30 Jul 2007 15:50:08 -0700
    From: David Brodbeck <gull at gull.us>

    > On Jul 30, 2007, at 3:25 PM, f-myth-users at media.mit.edu wrote:
    > > If you want -maximal- isolation, you hook a motor to a generator
    > > and you can get better isolation than even an isolation transformer
    > > will give you... :)

    > And there are sites that do that.  But it has its own unique issues.   
    > Now instead of the massive impedance of the power grid to smooth out  
    > quirks in your loads, you have a relatively small generator.  You  
    > become vulnerable to spikes created on your OWN site by big loads  
    > turning on and off.  Small generators can also easily lose voltage  
    > regulation in the presence of highly capacitive loads, which happen  
    > to include many computer power supplies.  Third-order harmonics  
    > created by switching supplies can wreak their own unique kind of  
    > poorly-understood havoc, as well.

Yes; I wasn't serious about this, for all of the above reasons.

(I'm waiting for the first instance of the real grid going into
oscillation from the negative resistances of all those switching
power supplies.  So far, the load is still vastly positive R with
lots of reactance, but someday... :)


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