
Originally Posted by
12vdc
Online ups(or sometimes called double conversion) has its inverter always on regardless of mains input condition which means the output voltage is fixed regardless of mains input fluctuations.
The backup typeUPS(also called standby or line interactive)adjust output voltage only at a certain upper and lower threshold of the mains, ex: mains V dips to 190V, inverter engages to correct the output V to 220V, same happens when input voltage goes beyond 240V. The time in between turning on the inverter means delay. Delay is always a problem, even humans don't want delays.
Now, comparing the delays. A backup UPS using a solid state relay or mechanical contact will respond at about 2-20ms while the typical potentiometer-type AVR reacts in half a second or more depending how slow the wiper and motor movement. Online UPS delay is 0(zero) ms.