OM226142 rev C
18
3.2 BATTERY OPERATION
In the event of mains failure, or rectifier failure, the inverter is no longer supplied by the
rectifier, so the battery, that is connected to the DC intermediate circuit, is called up
immediately and without interruption to supply the load. The battery voltage drops as a
function of the magnitude of the discharge current. The voltage drops has no effect on the
inverter output voltage since it is kept constant by varying the PWM modulation.
As the battery approaches the discharge limit an alarm is activated. In case the power is
restored (even using a diesel generator) before the limit is reached the system switches
automatically back to normal operation, if not, the inverter shuts down and the load is
transferred to the bypass (bypass operation). If the bypass mains is not available or
outside the tolerance range the complete system shuts down as soon as the lowest battery
level is reached.
As soon as the power is restored the rectifier charges the battery, and, depending on the
depth of the discharge, the charging current is limited by means of the battery current
limitation.
Picture 14 – Battery operation
Section Status Further explanation
Rectifier Mains NOT available or outside the tolerance range
RCB CLOSED
Rectifier OFF
Battery available and within the tolerance range
BCB CLOSED
Inverter ON
Bypass Mains available
and within the tolerance range (may be
outside the tolerance range)
SBCB CLOSED
BYPASS SWITCH “NORMAL”
Static Switch SSI ON
Static Switch SB OFF
OCB CLOSED
MBCB OPEN
Output Voltage available and within the tolerance range
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