Common Causes of Undervoltage Faults:

1. Insufficient Input Voltage: If the AC voltage supplied to the drive is lower than the required level, it can lead to an undervoltage fault. This might occur due to power supply issues, fluctuations in the electrical grid, or problems with the input wiring.
2. Rectifier Issues: The rectifier within the drive converts AC input voltage to DC. If the rectifier is damaged, malfunctioning, or overloaded, it can cause a drop in DC bus voltage.
3. Fuse Failure: A blown fuse in the input circuit can also result in an undervoltage fault.
4. Loose Connections: Poor or loose connections in the power supply or motor cables can lead to voltage drops.
5. Overload: If the drive is overloaded beyond its rated capacity, it can draw excessive current, causing the DC bus voltage to decrease.

Troubleshooting Steps:

1. Check Input Voltage: Ensure that the AC voltage supplied to the drive is within the specified range. Use a voltmeter to measure the voltage at the drive's input terminals.
2. Inspect Rectifier: If the input voltage is correct, examine the rectifier for any signs of damage or overheating.
3. Check Fuses: Replace any blown fuses in the input circuit.
4. Tighten Connections: Verify that all connections, including those to the motor and power supply, are secure and free of corrosion.
5. Reduce Load: If the drive is overloaded, try reducing the load to see if the fault is resolved.
6. Check Drive Parameters: Ensure that the drive parameters are set correctly. Incorrect settings can sometimes contribute to undervoltage faults.