D: Parallel Operation - Toshiba 1700 Series User Manual

Appendix D: Parallel Operation
The 1700 Series UPS offers a standard feature that allows the unit to
operate with very low input voltage without de-rating the output power. If
the input voltage drops below a certain point the unit will switch to
parallel mode. Parallel mode means that the unit is using the available
input voltage and supplementing with battery power. Because battery
power is being used, the time the unit can operate in parallel mode is
limited. However, the time will be longer than that available when the
unit is operating on battery power alone. The point when the UPS will
enter parallel mode will vary depending on the output load. The following
graph shows the various stages based on full output load and 75%
output load.
As shown by the graph the lower the output load the lower the input
voltage can go before parallel mode is activated. However, the minimum
input voltage will always remain at 50% (60VAC for a 120VAC system).