Emerson Liebert NXL series Operation And Maintenance Manual page 87

Liebert NXL UPS
Event Message Event Definition
Low Power
The output power factor is low.
Factor The output power factor is less than
70% leading or lagging. A simplified
explanation of power factor is the ratio
of energy being supplied to energy being
used by the load. For a given load, the
current output of the UPS goes up as
power factor decreases.
This results in the UPS output being
derated.
For example, study the following:
Load = 100 kw @ 400V
amps = kw X 1000 / volts X power factor
X 1.73
(square root of 3)
100kw X 1000 = 100000
400volts X .9PF X 1.73 = 622
100000/622 = 160 amps
Now, replace the .9 power factor (typical
computer load power factor) with .7
power factor:
100kw X 1000 = 100000
400volts X .7PF X 1.73 = 484
100000/484 = 207 amps
The load remains the same, but the
current required to supply it is roughly
30% higher. The extra current is wasted
energy that can result in nuisance trips
of breakers, overheating of cables, and
other unwanted conditions. The UPS
cannot control the output power factor.
Main Control
The UPS has transferred to Bypass due
Fault
to a loss of communications with the
Main Controller.
All Transfers, Startup, Shutdown, and
Metering screens are locked out.
The Controls attempt to reestablish
communications but will not return the
load to inverter automatically.
Liebert NXL alarm and status messages (continued)
Page 87
Operation and Maintenance Manual 250-300-400-800kVA
Recommended Action
Press "SILENCE" to silence the audible
alarm.
Evaluate the load on the UPS. For more
information, contact your factory-
authorized service provider.
Press "SILENCE" to silence the audible
alarm.
Contact your factory-authorized service
provider.
If communications are reestablished, the
One-Line Display will be restored;
however, Liebert does not recommend
attempting to return the load to inverter
until a service visit has been made and
action taken to determine why the fault
occurred.
Action will involve resetting the UPS
controls by removing and then reapplying
control power.
Therefore, it will be necessary to utilize
maintenance bypass, either by closing the
Q3 internal bypass breaker, or by closing
the optional external Maintenance
Bypass Breaker (MBB). Liebert does not
recommend the user, or operator, attempt
this without first speaking with an
authorized service associate from Liebert.