Modes Of Oper4Tion; Through The Ups Module; Static Bypass Line; Maintenance Bypass Line - Liebert 300 series Installation, Operaton & Maintenance Manual

Maintenance Bypass Line

Line conducting electricity directly from
input power to critical load during
maintenance or whenever UPS is not
completely operational. Maintenance Bypass
Line is connected when rotary switch is in
Position 1, 2, or 3.
External Maintenance Bypass Cabinet
An external maintenance bypass line in a
matching cabinet with switching
mechanism, and optional circuit breakers
and optional bypass transformer, to totally
isolate the UPS module from the electrical
system.
Slim-Line Distribution Cabinet
A cabinet extension of the UPS module to
enclose one or two 42-pole panelboards, with
a main circuit breaker for each panelboard.
1.2 MODES OF OPERATION
The UPS provides the following three power
paths between the utility source and the critical
load.

Through the UPS Module

l

Static Bypass Line

l
. Maintenance Bypass Line.
1.2.1 Through the UPS Module
During normal operation, the output of the UPS
Module inverter is used. Input AC power to the
UPS is converted to DC by the rectifier/charger.
The DC power charges the UPS battery and
provides input power for the inverter. The
inverter converts the DC power to conditioned
AC power which supplies the critical load. The
conversion-inversion process eliminates voltage
transients existing in the input power before it
reaches the critical load. If input power is
interrupted, the battery will immediately supply
the DC power required by the inverter to
maintain continuous AC power to the load. A
fully charged battery will provide power for the
reduced load.
1.2.2 Static Bypass Line
The Static Bypass Line provides an alternate
power path during an overload condition or UPS
fault. If the load demands more power than the
inverter can supply (an overload condition), the
control system automatically energizes the
static transfer switch to transfer the load from
the UPS Module to the Static Bypass Line. If
the internal control system detects a fault in the
UPS Module while it is supporting the load, the
static transfer switch transfers the load without
interruption to the Static Bypass Line, thereby
maintaining continuous power to the critical
load.
1.2.3 Maintenance Bypass Line
The Maintenance Bypass Line is a hard-
wired line through the UPS which supplies the
critical load with unconditioned power when the
Rotary Switch is in Position 1, 2, or 3. The
purpose of this line is to route power to the
critical load during start-up or while the UPS
Module is de-energized for maintenance. The
Maintenance Bypass Line can only be selected
manually, using the Rotary Switch. When the
Rotary Switch is in Position 4, the internal
control system determines which of the other
two paths supplies power to the load.