Powerware Uninterruptible Power Supply SOLA 4000 - Manual (Page 10)

SOLA 4000 - General System Description
JUE 401264 10
1.7 Maintenance Bypass
The maintenance bypass function is to supply power directly to the
connected load during UPS maintenance. The bypass consists
essentially of one switch IBY.
With SOLA 4000 series UPS systems, switching from different
operating modes to maintenance bypass can be performed without
interruption. With the maintenance bypass on, the UPS system
may be completely switched off, thus permitting maintenance work
to be carried out safely ( there will only be voltage at the input and
output terminals and their connections to the circuit-breakers).
In order to prevent erraneous switching of the maintenance bypass
switch IBY that could possibly cause parallel connection of the
bypass line and the inverter line, IBY is electronically intercon-
nected with the static inverter switch SSI. Thus, during actuation of
IBY, switch SSB will be closed and switch SSI opened automati-
cally, preventing parallel operation of the maintenance bypass
network and the inverter.
As an option, an external wall-mounted no-break maintenance
bypass switch (see FIG. 1.6.1) may be supplied by SOLA.This
switch provides simple one-step transfer to maintenance bypass
(version 1) without the possibility of erraneous switching and
without interruption to the load.For the version 2 type maintenance
bypass, an additional position is provided in order to completely
isolate the UPS with the one bypass switch.In this way, the UPS
may be isolated totally from all supply by switching off the input
supply to the UPS.
1.8 Hot-Standby Systems
A hot-standby UPS system basically consists of two (or more)
single UPS units which operate independently of each other. Any
one unit can be feeding the load at any time.
• All units are continuously in operation; but only one is supplying
the load, at any one time.
• In case of a failure in the unit currently supplying the load,
another unit is ready to takeover the load without an interrup-
tion on the output side. i.e. the load is still supplied with condi-
tioned and stabilised power.
• The load is supplied by the static bypass, only if there is no
inverter ready in the system to takeover the load.
1 UPS Assembly