Vertiv Liebert EXM - 6.18 Static Bypass Switch

Vertiv™ | Liebert® EXM
™
50-250kVA, 480V, 60Hz User Manual | 72
The Liebert
®
EXM
™
operates in the modes shown in Table 12. This section describes various kinds
of operating procedures under each operating mode, including transfer between operating
modes, UPS setting and procedures for turning on/off inverter.
As shown in SL-25656, the Liebert
®
EXM
™
Battery Cabinet manual, the AC utility source is
supplied through the input breaker, and the rectifier converts the alternating current into DC
power. The inverter converts the AC power from the utility—or DC power from an optional
External Battery Cabinet—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 using the optional Liebert
®
MBC
™
.
6.18 Static Bypass Switch
The circuit block labeled “Static Bypass” contains an electronically controlled switching circuit
that enables the critical load to be connected to either the inverter output or to a bypass power
source via the static bypass line. During normal system operation, the load is connected to the
inverter and the inverter contactor is closed; but in the event of a UPS overload or inverter failure,
the load is automatically transferred to the static bypass line.
To provide a clean (no-break) load transfer between the inverter output and static bypass line,
the static switch activates, connecting the load to bypass. To achieve this, the inverter output and
bypass supply must be fully synchronized during normal operating conditions. This is achieved
through the inverter control electronics, which make the inverter frequency track that of the
static bypass supply, provided that the bypass remains within an acceptable frequency window.
AVERTISSEMENT
Risque d’arc ou de décharge électrique pouvant entraîner des dommages matériels, des
blessures et même la mort.
L’armoire Liebert
®
EXM
™
contient des tensions élevées à l’interne. L’utilisateur ne peut ni
entretenir ni remplacer des composants accessibles uniquement en ouvrant le couvercle
de protection avec des outils.
Seul du personnel de service qualifié et dûment formé est autorisé à retirer les couvercles
de protection.
Table 12 UPS operating modes
Operating Mode
Description
Normal Mode
NORMA
L
UPS powers the load
Bypass Mode
BYPAS
S
The load power supply is provided by the static bypass. This mode can be regarded as a
temporary transition mode between the normal mode and maintenance bypass mode, or a
temporary abnormal operating status.
Maintenance
Mode
MAINT
UPS shuts down, the load is connects to the mains through the Liebert
®
MBC
™
. In this mode
the load is not protected against abnormal input utility power.
NOTE
When the UPS is operating in static bypass mode or on maintenance bypass, the connected
equipment is not protected from power failures or surges and sags.