Page 164 - Uninterruptible Power Supplies

Static Uninterruptible Power Supplies
162 Chapter Five

UPS NR. 1

~ – ~ ~
– + ~ ~

UPS NR. 2

~ –
MAINS ~ ~
INPUT – + ~ ~ OUT

UPS NR. _ _

~ – ~ ~
– + ~ ~

AUXILIARY
MAINS
Figure 5.19

operation of the system. Clearly, under certain conditions, a heavy fault
current could conceivably occur, and in practice the high-speed static
switches shown in Fig. 5.17 will isolate the faulty module. Sensing the
fault is of paramount concern and one chosen way is to use a voting sys-
tem to ascertain the faulty module. In this system all modules send a
constant stream of signals to a common control PCB, which in turn
ensures correct operation and isolation of the faulty module. In many
designs these interconnecting signal control cables are duplicated to
ensure guaranteed operation.

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