On 1/27/21 1:42 PM, Carlos E. R. wrote: The UPS never actually failed, except for a time or two when the battery bank needed to be replaced.
I've had some of my own UPSs fail after several years. But one time, a few years ago, when I was working for a telecom company. I got a call that their fibre connection had failed. When I got there, the entire 3 cabinet lineup was down, due to a failed UPS. BTW, a "UPS" we had at work many years ago, was an motor turning an alternator and an 8 ton flywheel. When the power failed, a clutch would connect a huge diesel engine to the flywheel to start it and take over the load. When that diesel was running, you could feel it throughout the building. That system also produced power that was slightly lower frequency than the mains due to the induction motor used to run it. IIRC, there were 4 of those systems. Later on, turbines were used.