Vertiv Liebert EXM2 - UPS Power Supply Switch Configuration

Parallel SystemThe control logic system constantly monitors load requirements and controls the power supplied by each
UPS module. In the event that 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.
M aintenance bypass
The UPS has a second bypass circuit, i.e. maintenance bypass, 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.
W A RN IN G! If the U PS system is com posed of tw o or m o re U PS m odules and when the load
capacity exceeds the single m odule capacity, d o not use the internal m aintenance bypass
switch.
2.2.4 UPS Power Supply Switch Configuration
The UPS has four switches: rectifier input switch Q1, bypass input switch Q2, maintenance bypass switch Q3, and output
switch Q5.
Figure 2.2 on the next page describes the block diagram of the UPS module. The UPS has split bypass configuration (i.e., the
bypass adopts independent mains input) and common input configuration. If the system adopts common input configuration,
the UPS has shorting copper bar of common input configuration, and the bypass input switch (Q2) and rectifier input switch
(Q1) would be linked together. If the system adopts split bypass configuration, just remove the shorting copper bar of
common input configuration of the UPS.
During the normal operation of the UPS, except for the maintenance bypass switch Q3, other switches shall be closed.
2 Overview
11
Vertiv™ Liebert® EXM2 UPS User Manual