[Nut-upsdev] Questions on the state of the UPS market

[Arjen de Korte]

Citeren Robert Woodcock <rcw at debian.org>:

[...]

> Some of the fancier ones in category #2 are "line-interactive", which
> try to buck or boost voltage to maintain output compliance without
> going on battery. But they still pass whatever hiccups get through
> the filter to your equipment. You may or may not see any that do this
> for under $200. They'll use words like "line-interactive", "buck/boost",
> "AVR", etc., in their specs.

Most (if not all) consumer grade UPS devices on the market today are  
"line-interactive", the "off-line" versions are getting rare. Even in  
regions with rock-steady mains supplies, where the risk of brown-outs  
is non-existant, you won't find many without AVR. The reason is  
probably that this is an incredibly cheap function to add to an  
"off-line" UPS. In all units that I have examined, the same  
transformer that is used for the inverter is used for the battery  
charger and AVR function. If there is a micro-controller on board, all  
it takes to add AVR to a typical "off-line" UPS is one or two  
additional relays (and these are dirt cheap if you buy them in  
volume). You will find offers for 500 - 700 VA devices for under US$  
50 already.

[...]

>> 1b: Is the SPS in fact dead as a technical category?  If not, why not?
>
> I'd say it's more pervasive now than in 2005. Price/profits/ignorance.

The only real disadvantage of the "off-line" and "line-interactive"  
topology, is that you have no indication about the correct operation  
of the inverter and switch-over relays until you need them.  
Switch-over times (2 - 10 ms) that are commonly mentioned as a  
disadvantage of this topology are a non-issue for switched mode power  
supplies found in virtually every device that will be connected to it.  
These are well within the range that switched mode power supplies must  
be able to cope with in everyday life. I really doubt the benefits of  
the "on-line" topology outweigh the disadvantages for consumer use,  
like lower efficiency and usually the need for active cooling (fans).  
For most SOHO applications, this topology will be just fine and I  
don't see this changing anytime soon.

Best regards, Arjen
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