Powerware Uninterruptible Power Supply SOLA 4000 - Manual (Page 11)

SOLA 4000 - General System Description
JUE 401264 11
1.9 Parallel-Redundant Systems
A parallel UPS system consists of 2 to 8 single UPS units con-
nected in parallel, sharing the load current equally. Each unit has an
individual static bypass, thus ensuring also redundancy of the static
bypasses in a redundant system, i.e. if one static bypass should fail,
the bypass system will still be available.
There is no common electronic device for the parallel system. Each
unit has its own parallel-operation electronics that controls all of its
functions, thus ensuring perfect redundancy.
1.10 Parallel Systems
This is identical to the configuration in section 1.9 except that the
rated load is normally equal to the rating of the UPS and there is
therefore no redundant unit. UPS units of different kVA ratings may
be connected in parallel in this configuration, proportionally sharing
the load.
Note that the parallel configuration is identical to the parallel-
redundant configuration if the load is reduced to a value such that
the system minus one (or more) units is capable of supplying the
reduced load. Therefore one (or more) units become redundant and
the control is identical.
FIG. 1.8 - Parallel Operation - Block Diagram
1 UPS Assembly