Liebert NX series Operation & Maintenance Manual page 35

Table 8 UPS status messages (continued)
No. Event Message
30 Bypass Abnormal
31 Inverter Asynchronous
32 Inverter Fault
Description / Suggested Action (if any)
This alarm is triggered by an inverter software routine when the amplitude or frequency of
bypass voltage exceeds the limit.
The amplitude and frequency limit of bypass voltage are set via the configuration software
(By default, +15% as maximum amplitude, -20% as minimum amplitude, ±10% as
frequency range).
This alarm will also be activated by "Bypass disconnect open", "Bypass phase reverse" or
"Mains neutral lost" alarms.
This alarm automatically resets once the bypass voltage goes normal.
Suggested Action
First check if there are some relevant alarms such as "Bypass disconnect open", "Bypass
phase reverse" and "Mains neutral lost". If they appear, solve them first.
1. Then verify that the bypass voltage and frequency displayed on the panel is within the
bypass limit. Note here the rated voltage and frequency are specified by "Output
voltage level" and "Output frequency level" respectively. And once this alarm occurs,
there is a hysteresis loop of 5V in phase voltage and 0.1Hz in frequency to recover.
2. If the displayed voltage is believed to be abnormal, then verify the bypass voltage and
frequency presented to the UPS. Check the external bypass supply if it is found to be
faulty. 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 customer's
agreement.
3. If Step 2 shows the displayed bypass voltage and frequency are quite different from the
actual bypass voltage and frequency, measure the signal to the U1 control board. If this
is correct then replace the U1 control Board; else check the wiring connections to M4
measure board, and if this is correct replace the M4 measure board.
This alarm is triggered by an inverter software routine when the inverter and bypass
waveforms are misaligned by more than 6 degrees in phase. This alarm resets
automatically once the condition is no longer true.
Suggested Action
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. If it is too distorted, ask the customer to
verify and seek any possible measurements.
3. Verify the stability of the bypass frequency. If the stability is not ideal, try to increase the
inverter "slew-rate" via the configuration software in single unit system. Or ask the
customer to verify and seek any possible measurements in a parallel system.
This alarm is triggered by an inverter software routine when the inverter voltage or the
output voltage satisfies one of the following conditions:
1. The output voltage comes with a DC waveform above 390V.
2. The inverter voltage goes above 112.5% rating or below 75% rating for 3 cycles when
the inverter current is less than 70% rating.
3. The inverter voltage goes above 112.5% rating or below 87.5% rating for 1 second.
Suggested Action
First verify whether this alarm is "Inverter voltage fault" or "Inverter bridge short through
fault" by pressing the RESET button on panel.
1. If the fault cannot be cleared, this alarm is brought by "inverter bridge short through".
a. Power off the UPS, check the inverter IGBTs, also check the gate drivers. If there
are some errors, repair or replace them.
b. If the IGBTs are OK, then power on the UPS, and try to turn on the inverter without
load.
If the fault appears again, check the inverter voltage signals to the U1 control board from
the M4 measure board, and repair or replace as necessary.
If the fault disappears without load, check the loading conditions. Verify if there were great
impact or half-cycle loading conditions.
2. If the fault can be cleared, this alarm is brought by "inverter voltage fault ". Try to turn on
the inverter again without load, verify that the inverter voltage is at the normal value.
a. If the fault appears again, verify that the output voltage and regulation are set
appropriately via the configuration software. Reprogram them if necessary. Check
the inverter voltage signals to the U1 control board from the M4 measure board, and
repair or replace as necessary.
b. If the fault disappears without load, check the loading conditions. Verify if there were
great impact or half-cycle loading conditions.
29
UPS Status Messages