Liebert UPS System - Manual (Page 104)

Chapter 8 Parallel System
98
Note
At this time, the input and output terminals of this failed UPS unit are still energized.
Switch off the unit’s input and output circuit breakers if these terminals may be
touched during maintenance.
2. After repairing the failed UPS, connect it to the parallel operation system
again
After repairing the failed UPS, the procedures to connect it to the parallel operation
system are given below:
1) If this UPS unit’s input and output circuit breakers have been switched off during
maintenance, switch on them again;
2) Switch on this UPS unit’s Q1 and Q2;
3) Switch on this UPS unit’s battery switch QF1;
4) When this UPS unit’s rectifier starts (the rectifier indicator illuminates green),
press the “inverter start” button to start the inverter. If the inverter can be start, then
the UPS recovers to normal, otherwise switch off and isolate the UPS unit again
and repair it;
5) After the inverter starts, switch on Q5，this UPS unit will operate together with
other UPS units normally.
8.5.5 Emergency shutdown
In parallel operation system, if only one UPS unit needs to be shut down, the user
should press the “emergency shutdown” button on this UPS unit. If all the UPS
units need to be shutdown, connect all the “emergency shutdown” dry contacts of
the UPS units together and set up a “emergency shutdown” button for the whole
system. But the UPS units should be repaired separately. The operation procedures
are given in Chapter 6.
Method of setting up a “emergency shutdown” button for the whole system
A isolated multi-branch button should be used as emergency shutdown button,
pressing this button can switch off multi UPS units at the same time. The method is
shown in Fig. 8-6. That is, connect the control cables from the J12(pin 1 is normally
closed contact, pin 2 is central contact and pin 3 is the normally open contacts,
select the normally open and normally closed contacts according to control mode)
on the ULW2L61U2 board to the switch of the “emergency shutdown” button. In
order to avoid EMI, the EPO(emergency shutdown) cables must be shielded and
the shielded cables must be grounded at the EPO switch.