Emerson Liebert GXT4-700RT230 - Operating Principle

Chapter 1 Product Description 3
Liebert GXT4 UPS 700VA ~ 3000VA (230V) User Manual
1.4 Operating Principle
The operating principle of the UPS is illustrated in Figure 1-4.
TVSS & EMI/RFI
Filters
Rectifier/PFC Inverter
DC-to-DC
Converter
BatteryBattery Charger
Input Output
Dynamic Bypass
L1 L1
L2/N L2/N
G G
Figure 1-4 Operating principle diagram
The UPS is composed of utility input, TVSS and EMI/RFI filters, rectifier/PFC, inverter, battery charger, DC-to-DC
converter, battery, dynamic bypass and UPS output.
Transient voltage surge suppression (TVSS) and EMI/RFI filters
The Liebert GXT4 UPS has surge protection and filters that protect the connected load from power surges,
electromagnetic interference (EMI) and radio frequency interference (RFI). These features can minimize any surges
or interference present in the utility power. The filters also prevent surges or interference generated by the UPS from
adversely affecting devices connected on the same branch as the UPS.
Rectifier/Power factor correction (PFC) circuit
In normal operation, the Liebert GXT4’s rectifier/power factor correction (PFC) circuit converts utility power to
regulated DC power for use by the inverter while ensuring that the wave shape of the input current used by the UPS
is near ideal. Extracting this sine wave input current achieves two objectives:
 Efficient power use by the UPS
 Reduced reflected harmonics
This results in cleaner power being available to other devices in the building not being protected by the Liebert GXT4
UPS.
Inverter
In normal operation, the Liebert GXT4 UPS’s inverter utilizes the DC output of the PFC to produce precise, regulated
sine wave AC power. When utility power fails, the inverter receives DC power from the DC-to-DC converter. In either
operation mode, the UPS inverter is online, continuously generating clean, precise, regulated AC output power.
Battery charger
The battery charger utilizes energy from the utility power and precisely regulates it to continuously float charge the
batteries. The batteries are being charged whenever the Liebert GXT4 UPS is plugged in, even when the UPS is not
turned on.
DC-to-DC converter
The DC-to-DC converter raises the DC voltage from the battery to the optimum operating voltage for the inverter. This
allows the inverter to operate continuously at its optimum efficiency and voltage, thus increasing reliability.