[Nut-upsuser] Energy efficient UPS - anybody?

[Arjen de Korte]

Citeren devzero op web.de:

> i currently have an older powerwalker which constantly burns ~15W  
> for nothing. The transformer inside getting that hot that you don`t  
> like to touch it and i think 15W out of 50 is a little bit high and  
> that inside a plastic case looks a little bit dangerous to me, too.   
> since this ups is old anyway, i`d like to replace it with a better  
> one.

This kind of zero load power is typical for low frequency (LF) UPS  
designs that use the inverter transformer for charging the batteries  
and to power the monitoring circuit. Usually, you'd expect about 2-5%  
core/iron losses of the nominal power rating of a small transformer.  
So for a 500VA UPS (transformer), a no-load loss of 10-25W will be  
typical. You'll only find this kind of topology in cost sensitive  
(consumer) devices up to about 1000VA, where wholesale price is more  
important than efficiency.

[...]

> so, this is not a very nut specific question, but i have no idea  
> where this question is better placed, as i think HERE are the real  
> UPS experts :)

You should look for a small standby or line-interactive UPS using a  
high frequency (HF) inverter. For small UPS devices this is the most  
power efficient topology and usually meets the requirements for SOHO  
applications. The Eaton Ellipse ASR or MAX series would be a good  
choice, since they are one of the few vendors that actually support  
NUT. I'm not sure about their Protection Station series, but it  
probably also uses HF technology too.

Best regards, Arjen
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