Diesel generators are essential for providing reliable power in industrial, commercial, and remote applications. However, operators may occasionally encounter a low voltage alarm, which can cause unexpected shutdowns and disrupt operations.
Understanding the common causes of this alarm and following proper troubleshooting steps is important for maintaining stable generator performance and protecting connected equipment. This guide explains the typical causes of low voltage alarms and provides practical steps to help identify the problem.
Possible Causes of Low Voltage Alarm
1. Excessive Load or High Starting Current
Motors and other high-power equipment can draw several times their rated current during startup. This high starting current can cause a temporary voltage drop and trigger the low voltage alarm.
2. Insufficient Generator Capacity
If the connected load approaches or exceeds the generator's rated capacity, the generator voltage may drop when the load is applied.
3. Low Voltage Alarm Setting or Voltage Regulator Issue
Incorrect AVR settings or an improperly configured low voltage alarm threshold may cause the protection function to activate unnecessarily.
4. Unbalanced Three-Phase Load
Uneven load distribution or incorrect wiring connections can result in voltage differences between phases and may cause a low voltage alarm.
5. Load-Side Short Circuit or Ground Fault
A short circuit or ground fault in the load equipment or supply cables can cause a sudden increase in current, resulting in voltage drop and generator protection activation.
6. Site Wiring or Connection Issues
Loose terminals, incorrect wiring, or poor connections between the generator and connected equipment can also cause abnormal voltage behavior.
Recommended Troubleshooting Steps
- ○ Check the nameplate information and rated voltage of the connected equipment.
- ○ Measure generator voltage under no-load and load conditions to identify abnormal voltage fluctuations.
- ○ Confirm the load power and starting method of all connected equipment.
- ○ Inspect load cables and equipment for short circuits, ground faults, or damaged connections.
- ○ Gradually connect the load to identify which equipment may cause the voltage drop or alarm.
- ○ Check and adjust the low voltage alarm setting on the generator controller when necessary.
Post time: Mar-10-2026
