Powerware 9390, Руководство по установке и эксплуатации

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Understanding UPS Operation
6-6
Powerware
®
9390 UPS (40–80 kVA) Installation and Operation Manual
S
164201535 Rev A
During an outage, transfers to bypass are prohibited and for the safety of those who may
be working on the power lines upstream from the UPS, the back feed protection contactor
is opened, preventing system output voltage from bleeding across the static switch
snubber components to the bypass input source.
If the inverter is unable to support the load on the output of the system, to ensure the
load remains energized, the UPS will transfer the load to the internal bypass. The output of
the system will be transferred automatically to the internal bypass if abnormal conditions
occur on the output of the system. If the output of the system exceeds acceptable voltage
and frequency tolerances, the system is overloaded, or the Inverter fails the output of the
system will be transferred to the internal bypass. The transfer is initiated by turning on the
static switch and opening the output contactor K3. This kind of transfer is normally
referred to as a Make-Before-Break transfer. The transfer should take place in less than 4
mS (quarter cycle) to ensure loads on the systems output are not interrupted. The static
switch remains on until either the inverter is able to support the system output or the unit
is placed into a maintenance position where repairs can be made.
If the UPS initiates its own transfer to bypass for any reason other than operator
intervention, the UPS will attempt to restart the inverter (if not running already) and
attempt a retransfer back on line to support the output of the system. Three attempts will
be made within ten minutes to bring the inverter back online automatically before the UPS
will lock out any further attempts. After three attempts have been made, the UPS will
remain in bypass and an alarm condition will be enunciated. The UPS can also be
transferred to bypass using the front panel controls.
Bypass mode is a normal operating mode, and not an alarm condition. However, if the UPS
is unable to return to Normal mode following an automatic transfer to Bypass mode, an
alarm condition is recorded.