Chapter 7 Parallel System And LBS System 105
Liebert EXM 80kVA ~ 200kVA UPS User Manual
4. At this moment, the TOUCHSCREEN of each UPS displays ' Maint. Switch Closed'.
5. Disconnect the output switch Q5 of each UPS in turn, and the maintenance bypass can supply power to
the load.
Caution
When the UPS is in maintenance mode, the load does not have the mains abnormal protection.
6. Pressing the EPO button of each UPS stops the operation of rectifier, inverter, static switch and battery,
but this action will not affect the maintenance bypass power the load normally.
Note
In maintenance mode, the load is directly fed by the mains power instead of the pure AC power from the inverter.
7. Disconnect the rectifier input switch Q1 and bypass input switch Q2 of each UPS in turn.
At the moment, all the internal power supply is off and the TOUCHSCREEN does not display any more.
Warning
1. If the maintenance is required, wait 10 minutes for the internal DC bus capacitance discharging.
2. The parts of UPS circuits also have hazardous voltage, though the rectifier input switch, bypass input switch and
battery switch are disconnected. Therefore, the UPS maintenance is applicable to qualified personnel only.
7.3.3
Procedures For Isolating One UPS Module From Parallel System
Important
These procedures shall only be carried out by service personnel of Vertiv or under their guidance.
Warning
Before operation, confirm that the system capacity has redundancy to avoid system shutdown due to overload.
The following procedures apply when one UPS module must be isolated from the parallel system for repair
due to serious fault:
1. Pressing the EPO button stops the operation of rectifier, inverter, static switch and battery, but this
action will not affect other UPSs in parallel system to power the load normally.
2. Disconnect the external power mains switch, rectifier input switch Q1, external power bypass switch,
bypass input switch Q2, output switch Q5, BCB and single module external output switch.
3. Correctly connect the remaining parallel cables in other single modules, refer to
7.2.5 Parallel Cables
.
Warning
1. Post a label at the AC input distribution (generally far away from the UPS) to alert that the UPS maintenance is
being operated.
2. Wait 10 minutes for the internal DC bus capacitance discharging. Then the UPS is completely shut down.
7.3.4
Procedures For Inserting One Isolated UPS Module In Parallel System
Important
These procedures shall only be carried out by service personnel of Vertiv or under their guidance.
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