34 Chapter 4 Operator Control And Display Panel
Liebert APM 90 Integrated Modular UPS User Manual
Alarm
Explanation
Bypass Unable to Trace
This alarm is triggered by an inverter software routine when the amplitude or frequency
of bypass voltage is outside specifications. The amplitude threshold is fixed for
±
10%
rating. This alarm automatically resets once the bypass voltage goes normal.
1. First verify that the bypass voltage and frequency displayed on the LCD are within the
selected ranges. Note that here the rated voltage and frequency are specified by Output
voltage level and Output frequency level respectively.
2. If the displayed voltage is believed to be abnormal, then verify the bypass voltage and
frequency presented to the UPS. Check the external supply if it is found faulty
Bypass Abnormal
This alarm is triggered by an inverter software routine when the amplitude or frequency
of bypass voltage exceeds the limit. The amplitude threshold is fixed for
±
10% rating. This
alarm automatically resets once the bypass voltage returns to normal.
1. First check if there are some relevant alarms such as Bypass phase reverse and Mains
neutral lost. If they appear, solve them first.
2. Then verify that the bypass voltage and frequency displayed on the LCD are within the
bypass limits. Note that here the rated voltage and frequency are specified by Output
voltage level and Output frequency level respectively.
3. If the displayed voltage is believed to be abnormal, then measure the bypass voltage
and frequency presented to the UPS. If the bypass voltage and frequency are abnormal,
check the external bypass supply.
4. If the mains is likely to trigger this alarm frequently, the bypass limits can be changed
to a wider tolerance through the service configuration software
Inverter Asynchronous
This alarm is triggered by an inverter software routine when the inverter and bypass
waveforms are misaligned by more than six degrees in phase. The amplitude threshold is
fixed for
±
10% rating. This alarm resets automatically once the condition is no longer true.
1. First check if the alarm Bypass unable to trace or Bypass abnormal occurs. If so, solve it
first.
2. Verify the waveform of the bypass voltage
Inverter fault
Inverter output voltage outside specifications. Load transfers to bypass. The faulty power
module will shut down and open output relay, and the remaining power modules will
remain online
Fan fault
At least one of the cooling fans failed
Bypass STS Fail
At least one of the STSs at the bypass side is open or shorted. This fault is locked until
power-off
Output Fuse Fail
At least one of the inverter output fuses is blown. The inverter shuts down, and the load
transfers to bypass if the remaining power modules are insufficient to support the load
Control power 2 fail
The UPS is operating but the redundant control power is abnormal or not available
Unit Over load
This alarm appears when the load arises above 105% of the nominal rating. The alarm
automatically resets once the overload condition is removed.
1. Find out if this alarm is true by checking which phase has overload through the load (%)
displayed on the LCD.
2. If this alarm is true, measure the actual output current to confirm if the displayed value
is correct.
3. If yes, disconnect the non-critical load.
In a parallel system, this alarm will be triggered if the load is severely unbalanced