Power Supply User Manual

1800 Series User Manual
41
APPENDIX C: PARALLEL OPERATION
The 1800 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 illustrates the UPS’ transition from battery
to line power as the line voltage increases from 40% to 100% of normal.
Transition curves are shown for 75% and 100% output load.
As shown in 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 60% (72 VAC for a 120 VAC system).
Input Power (%)
Input Voltage (%)
75% Load
100% Load
Battery
AC Input
100
Parallell Running: Input Power vs. Input Voltage
85705540
80
0
20
40
60
120