Liebert NX UPS System user manual Bypass voltage exceeds the limit

Operator Control Panel and Display

Table 22	UPS messages (continued)
Message		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.
		This alarm automatically resets once the bypass voltage goes normal.
		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.
Bypass Abnormal		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.
		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.
		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.
Inverter Asynchronous		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.
Inverter Fault		Inverter output voltage beyond limits. Load transfers to bypass.
		The temperature of the inverter heat sink is too high to keep inverter running.
		This alarm is triggered by the signal from a temperature monitoring thermostat on the inverter
		bridge heat sink.
		The UPS will recover automatically after a 5 minute delay from the disappearance of the
Inverter Overtemp.		overtemperature signal.
		If the overtemperature condition is true, then check for and verify:
		1. high ambient air 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 STS Fail		At least one of the static switches of inverter side is open or short circuit. This fault is locked until
		power off.
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		This record is registered following an incorrect operation:
Output Fuse Fail		At least one of the inverter output fuses is blown. Inverter shuts down. Load transfers to bypass.
Control Power 2 Fail		UPS operates but Redundant Control Power is not available.
		The UPS is confirmed to be overload when the load arises above 105% nominal rating.
		The alarm automatically resets once the overload condition is removed.
		1. Confirm that the alarm is true by checking the load percent indicated on the LCD panel to
Unit Over load		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 unnecessary load and ensure the safety. In a parallel system, a severe load sharing
		error can also leads to the alarm.
		The UPS parallel system is confirmed to overload when the total load arises above 105%
		nominal rating for the set basic number of UPSs. The alarm automatically resets once the
		overload condition is removed.
System Over load		1. Confirm that the alarm is true by checking the system load percent indicated on the LCD
		panel 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 unnecessary load and ensure the safety. In a parallel system, a severe load sharing
		error can also leads to the alarm.

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