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OPM_LPS_3UO_30K_40K_0US_V010.doc Operating Manual LP 33 Series 30 & 40 kVA
Automatic bypass operation
In VFI (Voltage Frequency Independent) operation
mode, the load is permanently supplied by the
inverter but, in case of trouble on the inverter, or
when overload or short-circuit on the output
occur, if the mains voltage do not exceed the
admitted tolerances, the load is instantly
transferred to the mains through the automatic
bypass, taking advantage of the higher short
circuit power.
Fig. 3.2-3 Energy flow in automatic bypass operation
When the inverter recovers, the load will be re-transferred automatically to the inverter.
In case of parallel system
Each unit has its own bypass.
All the bypasses in the system work together, their control being managed in the same manner by
all units.
The units are continuously exchanging information before taking such decision.
In case the inverter of one unit fails, its bypass remains operating.
It is excluded only if the unit is separated from the common bus by opening its output switch Q1.
Mains recovery operation
As soon as the mains recovers, the rectifier starts
up automatically supplying the inverter and the
battery-charger recharges the battery.
In case the inverter has been shut down following
a complete discharge of the battery, when the
mains recovers the system start up automatically.
Fig. 3.2-4 Energy flow at mains recovery operation
When the energy stored in the battery is sufficient to ensure a minimum time of operation with the
actual load, in case of a future mains failure, the load will be retransferred to inverter (if selected VFI
Mode).
In case of parallel system
When the AC input power recovers, the rectifiers will start up sequentially according to their
number in the parallel system in order to avoid an initial inrush current.
The inverters will start up automatically, but only when the battery has recharged enough for a
minimum runtime with the present load.
When enough inverters to supply the load have been restarted, the load will be transferred from the
automatic bypass back to the inverter bus-bars.