8.3 Operation Procedures for Parallel System
Only one step should be carried out at time, and only after finishing this operation step of each UPS module, the next step can
be carried out.
8.3.1 Startup Procedures in Normal Mode
These procedures are applicable to start the UPS under total power-down state, which means the UPS or the maintenance
bypass switch has not supplied the load before. Make sure UPS has been completely installed and commissioned by the
engineer, and external power supply switch has been turned off.
W ARN ING ! T hese procedures result in m ains voltage being applied to the UP S outp ut
term inals.
W ARN ING ! If any load equipm ent is connected to the UPS ou tput term inals, check with the
user that it is safe to ap ply pow er. If the load is not ready to receive pow er, disconnect the
dow nstream load sw itch, and stick a w arning lab el on the co nnection p oint of the load.
Use the following procedures to turn on the UPS from a fully powered down condition.
1. Confirm that the total external maintenance bypass switches are disconnected. Open the front door of each UPS
in turn, ensure that the internal maintenance bypass switch Q3 is disconnected, while the input cables and
copper bars are reliably connected, and the parallel cables are firmly connected.
W ARN ING ! In parallel UPS configuration, all op erations related to disconnection or connection
of the m ainten ance bypass sw itch sh all be executed within three seco nds to avoid overload
situations & dam age to the maintenance bypass sw itch.
2. Close the total bypass input switches.
3. Close the output switch Q5, bypass input switch Q2, rectifier input switch Q1, and all external output isolating
switches (if any) of each UPS in turn.
At the moment, the system is powered on, and the startup screen pops up.
About 25 seconds later, confirm that the TOUCHSCREEN shows the rectifier power supply and the bypass power supply are
normal; if not, check whether the switches Q1 and Q2 are closed. Then the rectifier starts up, about 30 seconds after the
rectifier enters normal operation, the bypass static switch is closed.
4. When the rectifier start process is finished and the rectifier indicator goes solid green, close the external BCB.
5. For each UPS, manually turn on the inverter. As the inverter starts up, the whole UPS system will power the load.
8.3.2 Maintenance Bypass Procedures
W ARN ING ! If the UP S system is com p osed of m o re than 2 parallel UP S m odules, and the load
capacity exceed s the single m odule capacity, do n ot use the internal m aintenance b ypass
sw itch.
8 Parallel System and LBS System
133
Vertiv™ Liebert® APM Plus User Manual
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