Thread: UPS question
View Single Post
  #8 (permalink)  
Old October 14, 2012, 10:03 AM
westom westom is offline
Join Date: Apr 2010
Posts: 25

Originally Posted by NyteOwl View Post
Not all UPS output square wave to the items they power. While the raw inverter output is indeed a square wave, better units use shaping circuits to provide an almost sine wave output virtually all electrical appliances can handle.
A square wave is power that virtually all electornic appliances can handle. Electronics are required to be and are designed that robust. A shaping circuit still leaves most UPS outputs looking like a trapezoid with spikes - as in pictures below.

That square wave output is also called a pure sine wave. How pure? Only useful recommendation says how 'pure' with numbers such as %THD. Why do so few discuss %THD? The manufacturer often will not publish those numbers. Otherwise many would learn their 'pure sine wave' output was only square waves.

Due to how electornics are designed, then the 'dirtiest' UPS output is also ideal power. Meanwhile, UPS manufacturers only say to not power a power strip from that UPS. They never really say why. But these pictures (Tech Tip 03 from an AC utility) of a UPS output does:
Tech Tip 03 - Indiana Business-Duke Energy

Another posted the output from his sine wave UPS:

Ideal power for any electronics. But can also damage strip protectors.

How much for a truly pure sine wave UPS. On the order of $1000. So that one can use a $90 power strip? Better is to use the $7 non-protector power strip.
Reply With Quote