11
Multiple UPS Operation (Parallel)
(continued)
Back-Up Mode
In this mode, utility AC input power has failed. Since the UPS Systems operate continuously on-line, their connected battery modules instantly
(with zero transfer time) supply DC power to their inverters. Their inverters, in turn, transform DC power into clean, stable AC output power for
the connected equipment load.
Reserve AC Input Supply Mode
In this mode, the power modules' inverters have encountered one of several abnormal operating conditions including overtemperature, continual
overload, shorted output or depleted battery power. The power modules automatically shut down their inverters to prevent damage. In order to
bypass their inverters, the power modules automatically transfer to a reserve AC input source to support the connected equipment load. (Note: since
the power modules' inverters are bypassed in this mode, the UPSs will not be able to switch to Back-Up Mode in the event of a power failure.)
After the power modules detect that abnormal operating conditions are over, they automatically reactivate their inverters and switch back to the
mains AC input source to support the connected equipment load.
