Bypass - Liebert APM 150 User Manual

2 Chapter 1 Overview
Input
Input
Mains
Mains
input
input
Input switch
Input switch
The UPS provides independent battery charger, and uses advanced temperature compensation technology to
prolong the battery life. The inverter uses high power IGBT switching and advanced SVPWM design to
reconvert the DC busbar voltage back into an AC voltage waveform.
During normal operation, both the rectifier and inverter sections are active and provide regulated load power
whilst simultaneously charging the battery. In the event of a mains power failure, the rectifier becomes
inoperative and the inverter is powered solely from the battery. Critical load power is maintained under these
conditions until the battery is fully discharged, whereupon the UPS shuts down. The end of battery discharge
is assumed when the battery voltage falls below a preset value.
The period for which the load can be maintained following a mains power failure is known as the system's
autonomy time and is dependent upon both the battery A/Hr capacity and the applied percentage load.

1.2.2 Bypass

The static switch and automatic inverter switch shown in Figure 1-1 contain an electronically controlled
switching circuit that enables the load to be connected to either the inverter output or to a bypass power
source through the static bypass line. During normal system operation, the load is connected to the inverters;
but in the event of a UPS overload or inverter failure, the load is automatically transferred to the static bypass
line.
During normal operating conditions, the inverter output and bypass supply must be fully synchronized so as to
achieve a clean (no-break) load transfer between the inverter output and static bypass line. The
synchronization between the inverter output and static bypass is achieved through the inverter control
Liebert APM 150 Integrated UPS Single Module And Parallel System
Maintenance switch
Maintenance switch
Rectifier Rectifier
Charger
Charger
Rectifier
Rectifier
Charger Charger
Battery
Battery
Figure 1-1 Block diagram for operating principle of single module
Maintenance bypass
Static switch Maintenance bypass
Inverter Inverter
Automatic
Automatic
inverter switch
inverter switch
5 power modules
Inverter
Inverter
Automatic Automatic
inverter switch
inverter switch
User Manual
Output
Output
UPS
UPS
output
output
Output switch
Output switch