On Feb 17, 10:41*am, Tegger wrote:
jamesgangnc wrote :

I assume the smaller
ones keep costs and heat down by not running the power through a power
supply and inverter 100% of the time. *Thus they have to switch
sources.

Correct. They feed line-voltage until that voltage fails to meet certain
pre-defined criteria. At that point the battery/inverter is switched-in.
The switching time is on the order of milliseconds, short enough that the
gap isn't noticeable to the equipment.

Maybe older UPS's used caps to bridge the gap if the switches were too slow
to be invisible to the equipment. I'm guessing here.

--
Tegger

You can't use a cap cause how would that work? Caps don't store ac.
The inverter isn't on until it decideds to switch.