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OPM_LPS_3UO_30K_40K_0US_V010.doc Operating Manual LP 33 Series 30 & 40 kVA
3.3 RPA PARALLEL SYSTEM
The RPA (Redundant Parallel Architecture) allows to extend the unit to a parallel system with 2, 3, or 4
units LP 33 Series connected on the same bus, which ensure the highest reliability rate and increase the
power availability.
Parallel system for power capacity
Two or more units can be paralleled in order to
achieve output power superior to the maximum
power delivered by a single UPS unit.
The maximum total load shared between the n
parallel units can achieve the 100% of the
installed nominal power system.
In the event of one unit fails, the load will be
suddenly transferred to the mains by the
bypass.
Parallel system for redundancy
The parallel system can be defined redundant
only in case the nominal power rating of n-1 units
of n parallel units is sufficient to supply the
required load power.
LPS33U_030-040_RPA system_GE_01
LP 33 Series
1
RPA
Board
LP 33 Series
2
RPA
Board
LP 33 Series
3
RPA
Board
LP 33 Series
4
RPA
Board
F2F1 F3 F4
UTILITY INPU
T
LOA
D
Fig. 3.3-1 RPA system diagram
The load in a parallel redundant system, is equally shared by n units connected on the output bars.
Should one of the parallel units trip off-line, the remaining (n-1) units will share the load maintaining the
applications protected by inverter until the normal situation restores.
Load sharing between parallel units
The control bus exchanging the data between the microprocessors of the paralleled units provide for a
constant proportional load sharing in every load condition.
Management and synchronization of the parallel system
All the units are identical without master and slaves.
One unit is arbitrarily selected as the reference (the first unit connected on power bus) being this unit the
first synchronized with the mains voltage, and all the other units synchronize with the first one.
In case the reference unit fails or it is excluded from the parallel power bus any other unit will take over
the reference role.
The AC input power source of all the bypasses must be the same for all the units of the parallel system
excluding any phase shift between them.
Control bus of the parallel system
A high-speed serial bus, guarantees communication, synchronization and load sharing between the
UPS modules.
Each module controls it’s own function, while the Master (each unit can be Master) controls and
commands the status of the system.
NOTE !
The parallel system exclude more rectifiers connected on common battery.
No transformers, fuses or automatic circuit breakers should be inserted between the
unit’s output and the load common bus bars.