Powerware Uninterruptible Power Supply SOLA 4000 - Manual (Page 64)

SOLA 4000 - Operation
JUE 401266 64
4 Operating Modes Parallel and Parallel/Redundant
Operation
4 OPERATING MODES PARALLEL AND
PARALLEL/REDUNDANT OPERATION
4.1 Normal Operation
"Normal Operation" is the standard operating mode of the UPS if
the system load is at its nominal value or the system is pro-
grammed in a way that all units remain on-line. Otherwise see
section 4.2.
• Mains power is present
• The rectifiers convert a.c. power to d.c. power used to charge
the batteries and feed the inverters
• The inverters convert this d.c. power to a.c. power used to feed
the connected load
• All units are sharing the load current uniformly. This is accom-
plished by means of the optional parallel-operation-electronic
pcb (IPR).
• All units operate completely independently of each other, each
unit supplying its respective share of the load.
4.2 Partial Load Operation
Single inverters that are not needed to supply the load can be
switched off automatically, thus saving energy and increasing
system efficiency.
• The load is supplied by the remaining inverters
• All rectifiers will continue to operate, charging also the batteries
of the units whose inverters have been switched off
• The system can be easily programmed for the minimum
number of units which must supply the load at any time.
• When the load is reduced, the units will individually decide
which one is to switch off automatically.
• The system may be programmed so that there will always be
one redundant unit on-line.
• If the load is again increased, or in the case of an inverter
failure, the unit(s) which have been switched off will automati-
cally switch on again to share the load.
• If the mains supply fails, all inverters will switch on and connect
to the load in parallel operation in order to maximise the battery
autonomy time, (see section 4.3)