Vertiv Liebert APM2 - UPS Power Switch Configurations

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UPS module failure

For single module system, In case of inverter failure and output fuse blowout, the load will automatically transfer to the bypass,

and the output power supply will not be interrupted. In this situation, contact the local Vertiv technical support.

For parallel system, In the event of a fault in a UPS module, it will automatically exit from the parallel system. If the system is

still capable of providing the required load, the remaining modules will continue to supply the load with no interruption. If the

remaining modules are no longer capable of fulfilling the power requirements, the load will automatically transfer to the

bypass.

Overload

If the inverter is overloaded or the inverter current remains outside the Specifications on page171 (see Table 12.6 on

page173) longer than the specified time, the load will automatically transfer to the bypass without power interruption. If both

the overload and the current are reduced to a level within the specified range, then the load will be transferred back to the

inverter. In case of output short circuit, the load will be transferred to the bypass, and the inverter will shutdown. Five minutes

later, the inverter will start up automatically. If the short circuit is removed at this point, the load will be transferred back to the

inverter. The transfer is determined by the features of the protective device of the system.

In the above two situations, the UPS screen will display alarm messages.

For parallel system, the control logic system constantly monitors load requirements and controls the power supplied by each

UPS module. If an overload condition is sustained for greater than a preset time, the load will transfer to the bypass, when the

number of active modules is unable to satisfy load requirements. The load returns to the inverter if the power is reduced to a

value that can be sustained by the number of active modules in the system.

Maintenance bypass

The UPS has a second bypass circuit, that is maintenance bypass (no switch model), which provides a safe working

environment for the engineers to provide regular maintenance or repair to the UPS system and at the same time provide

unregulated mains supply to the loads. The maintenance bypass can be manually selected through the maintenance bypass

switch, and it can be disconnected by turning the switch to OFF.

NOTE: If the UPS system has 2 or more UPS modules and when the load capacity exceeds the single module capacity,

do not use the internal maintenance bypass switch an external maintenance bypass breaker should be used instead.

2.2.4 UPS power supply switch configuration

The available configurations are:

• The UPS without any switch.

• The UPS equipped with single switch: maintenance bypass switch Q3.

• The UPS equipped with four switches:

• Rectifier input switch Q1.

• Bypass input switch Q2.

• Maintenance bypass switch Q3.

• Output switch Q5.

Vertiv™ Liebert® APM2 30 to 120 kVA Modular UPS User Manual

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