Bypass Mode_ Single Input_ Parallel Units - Delta Modulon DPH series User Manual

3.1.11 Bypass Mode_ Single Input_ Parallel Units

In parallel mode, when all inverters encounter abnormal situations such as overload, short
circuit, abnormal output voltage or low battery, they will automatically shut themselves down.
Meanwhile, if all UPSs detect the bypass AC source is normal, they will automatically switch
to bypass mode to protect the connected critical loads from power interruption. The critical
loads will be equally shared by all parallel units. After the abnormalities mentioned above
are eliminated, the UPSs will switch back to online mode from bypass mode. During bypass
mode, each UPS's tri-color LED illuminates yellow and each UPS's LCD shows the text
'Bypass' in the upper right corner. Please see Figure 3-13 for the path of electrical power
through the parallel UPSs in bypass mode.
1
Delta or non-Delta External Maintenance Bypass Cabinet
MAIN
Batteries
2
Delta or non-Delta External Maintenance Bypass Cabinet
MAIN
Batteries
Q3
UPS
Q1 Q0
Q5
Q3
UPS
Q1 Q0
Q5
(Figure 3-13: Bypass Mode Diagram_ Single Input Parallel Units)
Static Switch
Rectifier Inverter
Static Switch
Rectifier Inverter
3-13
3 Operation Modes
Q4
Q4
LOAD