Liebert NXC User Manual page 44

Operation and Display Panel
Alarm message
Soft start fail
Bypass unable to trace
Bypass protection
Inverter asynchronous
Inverter fault
Inverter overtemp.
Fan fault
Inverter relay fail
Bypass STS fail
Operation invalid
Neighbor bypass SSTS
fail
Output fuse fail
Unit over load
Byp. abnormal
shutdown
Inverter over current
44
Rectifier cannot start due to the DC bus low voltage
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
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
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 output voltage beyond limits. Load transfers to bypass
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
At least one of the cooling fans has failed
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)
At least one of the static switches of bypass side is open or short circuit. This fault is locked until power off
Incorrect operation
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
At least one inverter output fuse failure. The inverter shuts down, the load transfers to bypass
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
Both bypass and inverter voltages are abnormal. Load interruption
Inverter pulse width modulation module is over current
Description
User Manual 10H52188UM51 - Rev. 1 - 09/2011
Liebert NXC