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5.0 OPERATION
5.1 Introduction
Liebert’s NX™ Uninterruptible Power System system provides continuous, high-quality AC power to
your business-critical equipment, such as telecommunications and data processing equipment. The
NX UPS supplies power that is free of the disturbances and variations in voltage and frequency com-
mon to utility power, which is subject to brownouts, blackouts, surges and sags.
The NX utilizes the latest in high frequency, double-conversion pulse width modulation (PWM) tech-
nology and fully digital controls to enhance its reliability and increase the ease of use.
The standard NX consists of the UPS and internal batteries in a compact, single cabinet.
As shown in Figure 27, the AC utility source is input at CB1 and the rectifier converts the AC utility
into DC power. The inverter converts that DC power from the utility—or DC power from the batteries
—into AC power for the load. The batteries power the load through the inverter in the event of a
power failure. The utility source can also power the load through the static bypass.
If maintenance or repair of the UPS is necessary, the load can be switched without interruption in
service to the maintenance bypass.
Figure 27 Single unit block diagram with split-bypass input
5.1.1 Split-Bypass Input
Figure 27 illustrates the Liebert NX UPS in what is known as the split-bypass configuration wherein
a separate power switch to a dedicated bypass power source that also feeds the maintenance bypass
line connects the static bypass line. Where a separate power source is not available, the bypass and
rectifier input supply connections are linked.
!
WARNING
Hazardous Mains and / or Battery Voltage present behind covers.
No user-serviceable parts are located behind covers that require a tool for their removal. Only
qualified service personnel are authorised to remove such covers.
Bypass
Input
AC Utility
Input
UPS
Output
Neutral
Wire
SW1/D
SW1/C
Rectifier
Inverter
Battery
Charger
Discharge
Battery
Static Swich
Static Swich
SW1/A
SW1/B
CB1
Maintenance Bypass
Neutral
Wire