Liebert GXTRT Series Installation and User Manual
1-3 kVA UPS
Page 10
9/2005
Emerson Network Power
Product Introduction
1.4 Operating
Principle
The UPS operating principle is shown in Figure 1-9.
Figure 1-9 UPS schematic block diagram
The UPS comprises AC input, input filter (EMI and Class D Surge Protecting Device),
rectifier/PFC (power factor correction), DC/DC converter, inverter, bypass, internal charger,
battery and UPS output functional modules. The UPS uses DSP (digital signal processor) and
IGBT (insulated gate bipolar transistor) to ensure satisfactory performance and increase the
product reliability.
AC input:
contains AC input socket and input overcurrent protection switch.
Input filter:
contains EMI suppression filter and Class D SPD. It provides clean AC power to
the UPS.
Rectifier/PFC:
an important front-end processing functional module of the UPS. In Normal
mode, the rectifier/PFC circuit converts the AC input power to regulated DC power, while
ensuring that the wave shape of the input current used by the UPS is near ideal.
DC/DC converter:
it raises the DC voltage from the battery system to the optimum operating
voltage for the inverter when the UPS operates in Battery mode.
Inverter:
an important back-end processing functional module of the UPS. In Normal mode, the
inverter utilizes the DC output of the PFC circuit and inverts it into precise, regulated sinewave
AC power. In Battery mode, the inverter receives its required energy from the battery through
the DC/DC converter.
Bypass:
this module plays a very important role in enhancing the UPS reliability. In the event
of an UPS fault that will not lead to UPS shutdown, such as an over-temperature condition,
rectifier fault, inverter fault, the load will be automatically transferred to the bypass. In the
meantime, the LED indicators will indicate the fault type, and the fault information will be
reported through the communication ports.
Internal charger:
the internal charger of GXT1000-RT, GXT2000-RT and GXT3000-RT
standard power modules provides 1A charging current; that of GXT1000L-RT extended
back-up time power module provides 7A charging current; and that of GXT2000L-RT and
GXT3000L-RT extended back-up time power modules provides 8A charging current.
Battery:
Sealed maintenance-free lead-acid battery is used as the DC source of the UPS.
UPS output:
this module contains output EMI suppression filter and provides multiple AC
outputs for load.
Output Filter
Bypass
DC/DC
Battery
Input filter
Internal
charger
Input
Output
Inverter
Rectifier
/PFC
G
G
