44 User Manual 10H52188UM51 - Rev. 1 - 09/2011
Operation and Display Panel Liebert NXC
Alarm message Description
Soft start fail Rectifier cannot start due to the DC bus low voltage
Bypass unable to trace
This alarm is triggered by an inverter software program when the amplitude or frequency of bypass voltage
is beyond the normal range. The amplitude threshold is fixed for ±10% rating.
This alarm will automatically recover when the bypass voltage is normal.
1. First verify that the bypass voltage and frequency displayed on the LCD are within the selected range.
Note that the rated voltage and frequency are specified by the ‘Output Voltage Level’ and ‘Output
Frequency Level’ respectively.
2. If the displayed voltage is abnormal, please verify the actual bypass voltage and frequency presented to
the UPS. Check the external power if any fault is found
Bypass protection
This alarm is triggered by an inverter software program when the amplitude or frequency of bypass voltage
is too high or too low. The amplitude threshold is fixed for ±10% rating. This alarm will automatically recover
when the bypass voltage is normal.
1. First check if there are some relevant alarms, such as ‘Bypass Phase Reverse’, ‘Input Disconnect Fault’. If
so, solve them first.
2. Then verify that the bypass voltage and frequency displayed on the LCD are within the selected range.
Note that the rated voltage and frequency are specified by the ‘Output Voltage Level’ and ‘Output
Frequency Level’ respectively.
3. If the displayed voltage is abnormal, please verify the actual bypass voltage and frequency presented to
the UPS. Check the external power if any fault is found. If the utility is likely to trigger this alarm frequently,
the bypass limit can be changed a little larger through the configuration software according to the user
backfeed
Inverter asynchronous
This alarm is triggered by an inverter software program when the inverter and bypass waveforms are
misaligned by more than 6 degrees in phase. The amplitude threshold is fixed for ±10% rating. This alarm
will recover automatically when the alarm condition disappears.
1. First check if the alarm ‘Bypass Unable To Trace’ or ‘Bypass Protection’ exits. If so, solve it first.
2. Verify the waveform of the bypass voltage. If too distorted, ask the user to verify it and seek any possible
measurement
Inverter fault Inverter output voltage beyond limits. Load transfers to bypass
Inverter overtemp.
The temperature of the inverter heat sink is too high to keep the inverter running. This alarm is triggered by
the signal from a temperature monitoring thermostat on the inverter bridge heat sink. After the alarm is
cleared about 20 minutes, the inverter will start again automatically. The UPS will switch to bypass if the
alarm is triggered above one time in 2 hours, and power on the UPS manually and stwitch to inverter
working state after the alarm is cleared. Note: Wait for 20 minutes after the alarm is cleared, manual
power-on will be suceesful.
1. high ambient temperature
2. blocked cooling airway
3. any fan failure
4. prolonged inverter overload
Fan fault At least one of the cooling fans has failed
Inverter relay fail
At least one of the relays of inverter side is open or short circuit. This fault is locked until power off (for a 3-in
1-out system, possible causes for relay fault type: inverter fuse open, inverter IGBT open)
Bypass STS fail At least one of the static switches of bypass side is open or short circuit. This fault is locked until power off
Operation invalid Incorrect operation
Neighbor bypass SSTS
fail
At least one of the static switches of UPS unit bypass side in parallel system is open or short circuit. This fault
is locked until power off
Output fuse fail At least one inverter output fuse failure. The inverter shuts down, the load transfers to bypass
Unit over load
The UPS is confirmed to be overload when the load is above 105% nominal rating. The alarm automatically
recovers after the overload condition is removed.
1. Confirm that the alarm is true by checking the load percent indicated on the LCD to determine which
phase is being overloaded.
2. If the alarm is true, measure the actual output current to verify that the indications are valid. Disconnect
the unnecessary load and ensure the safety
Byp. abnormal
shutdown
Both bypass and inverter voltages are abnormal. Load interruption
Inverter over current Inverter pulse width modulation module is over current
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