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Liebert® EXM™ UPS 20-100kVA, 50/60Hz User Manual |
54
6.16
Operation
The Liebert
®
EXM operates in the modes shown in
. 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.
6.17
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.
NOTICE
Risk of power loss to connected load. Can cause damage to equipment.
The load equipment is not protected from supply aberrations, such as spikes, sags and failures, when the Liebert
®
EXM is
operating in Load on Bypass Mode.
WARNING
Risk of electrical shock and arc flash. Can cause property damage, injury and death.
The Liebert
®
EXM contains high voltages internally. Components that can only be accessed by opening
the protective cover with tools cannot be serviced or replaced by the user.
Only properly trained and qualified service personnel are authorized to remove the protective covers.
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
Descriptions
Load on Inverter
NORMAL
UPS powers the load
Load on Bypass
BYPASS
The load power supply is provided by the static bypass. This mode can be regarded as a temporary transition
mode between Load on Inverter Mode and Load on 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.
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