Bypass Mode_ Dual Input_ Parallel Units - Delta Modulon DPH Series User Manual

3.2.10 Bypass Mode_ Dual 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 3-24 for the path of electrical
power through the parallel UPSs in bypass mode.
UPS 1
BYPA.
MAIN
Batteries
UPS 2
BYPA.
MAIN
Batteries
(Figure 3-24: Bypass Mode Diagram_ Dual Input Parallel Units)
Q2
Static Switch
Q1
Rectifier
Q2
Static Switch
Q1
Rectifier
3-23
Inverter
Q3
Inverter
Q3
3 Operation Modes
LOAD