[time-nuts] UPS for my time rack
tn1ajb at nic.fi
Sat Oct 10 14:32:28 EDT 2015
Chris Waldrup kirjoitti:
> I have decided I'd like to get a UPS to put on the rack containing my
> Thunderbolt, the laptop that runs Lady Heather, and frequency
> counter. Has anyone had bad experience noise wise with the APC brand
> units like are available on Amazon and at Staples? I'd like to get
> one that doesn't generate lots of RFI. Thank you.
Get a line-interactive model which has inverter with classic iron
transformer. Line-interactive means that the inverter is not
continuously on when the mains voltage is OK, but the mais voltage is
routed thru multitap transformer which gives some filtering and enables
to fix under/overvoltage errors without turning on the inverter. When
there's blackout and inverter is really started the transformer will act
as a filter which reduces the HF interference caused by sine wave inverter.
You can recognize this kind of ups from treir weight. For example 2 kVA
model should weight more than 25 kg without batteries and more than 50
kg with batteries. You could look for example old APC SmartUPSes or APC
Matrix UPS, which has separate inverter unit, transformer unit and
battery units. Old SmartUPS'es may require float voltage modification
because their charging voltage tends to increase when aging. Without fix
it will kill the batteries too soon.
Worst case to buy is double conversion on-line model without any kind of
transformer. These are cheap but the inverter is on all the time and
it's output is not filtered. I have measured the output of these kind of
UPSes with spectrum analyzer and they are really horrible interference
sources. Not recommended if there's any kind of sensitive electronics.
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