Transferring Between Operation Modes - Liebert UPS System User Manual

1. Press the "inverter shutdown" to shut down the inverter and the system
transfers to bypass mode;
2. Switch off each UPS unit's Q1 and the QF1 of battery cabinet;
3. Switch on each UPS unit's Q3BP；
4. Switch on each UPS unit's Q2 and Q5；
AT this time, the user's load is totally dependent on the maintenance bypass of the
UPS; Common checking or maintenance work can be done after waiting for 8
minutes( that is, after the DC bus capacitor discharges to zero voltage).
If the UPS requires to be switched off totally, switch on the KBP，switch off all the
Q3BP switches, and then transfer the load to external maintenance bypass. Then
the replacing or capacity expansion operation can be done after disconnecting the
UPS input and output switches.
2. Shutdown in bypass mode
Follow the step 2-step 5 of "shutdown in normal mode" to shut down the UPS in
bypass mode.
3. Shutdown in battery mode
If the utility is unavailable, conduct the step 1 of "shutdown in normal mode", and
then switch off all the switches.
4. Shutdown in united operation mode
The procedures of "shutdown in united operation mode" is the same with that of
"shutdown in normal mode".

8.5.3 Transferring between Operation Modes

When the parallel operation system is in normal mode, it can transfer between
different operation modes, so the maintenance engineer can judge whether the
system operate normally according to the transferring condition. If all the sources of
the UPS is in normal range, conduct the following operations:
1. Normal mode to battery mode
Switch off all the UPS units' Q1 and Q2，the system will transfer from normal mode
to battery mode.
C hapter 8 Parallel System
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