AL003 Under Voltage Fault in Delta ASDA-B2 Servo Drive

AL003 Under Voltage in the Delta ASDA-B2 Servo Drive indicates that the main circuit input voltage has fallen below the allowable operating range. The servo drive continuously monitors the incoming power supply to ensure stable operation of the power electronics. If the input voltage drops below the rated protection threshold, the drive immediately generates Alarm AL003 and disables the servo output to protect the drive and motor.

This fault generally indicates a problem with the incoming power supply, power wiring, or incorrect input voltage, rather than a fault in the motor or encoder.

Possible Causes

• Main circuit input voltage is below the rated allowable voltage.
• No power supplied to the main circuit.
• Incorrect power input (wrong power system).
• Incorrect voltage wiring.
• Power switch is OFF.
• Blown input fuse or circuit breaker.
• Loose or damaged power supply wiring.
• Low mains supply voltage.
• Voltage drop caused by undersized power cables.
• Single-phase operation on a three-phase drive.
• Defective power supply equipment.
• Faulty rectifier or power circuit inside the drive.
• Internal DC bus charging failure.
• Internal hardware fault.

Solutions

• Verify the incoming supply voltage.
• Re-confirm the power wiring according to the Delta wiring diagram.
• Check that the input voltage matches the servo drive rating.
• Check the main power switch.
• Inspect input fuses and circuit breakers.
• Tighten loose power terminals.
• Repair or replace damaged power cables.
• Apply the correct power supply or appropriate serial adapter if required.
• Measure the voltage under load to detect excessive voltage drop.
• Inspect the main circuit for proper operation.
• Restart the servo drive after restoring the correct supply voltage.
• Contact Delta technical support if the alarm persists.

Additional Information

The Delta ASDA-B2 Servo Drive continuously monitors the main circuit input voltage to ensure reliable operation of the inverter and DC bus.

Alarm AL003 is generated when:

• The input voltage falls below the allowable operating range.
• The main circuit power supply is unavailable.
• An incorrect power system is connected.

According to Delta, the primary corrective actions are:

• Re-confirm the voltage wiring.
• Check the main power switch.
• Apply the correct power supply or serial adapter.

Operating the servo drive with insufficient input voltage can result in:

• Failure of the DC bus to charge correctly.
• Unstable servo operation.
• Unexpected motor shutdown.
• Inability to produce rated torque.

Unlike an Over Voltage Alarm, AL003 indicates that the available supply voltage is too low for safe operation.

Common Symptoms

• Servo drive displays AL003 Under Voltage.
• Servo output is disabled.
• Motor will not start.
• Alarm appears immediately after power-up.
• Alarm occurs during supply voltage dips.
• Main power indicator may be off or unstable.
• DC bus voltage is lower than normal.
• Servo cannot produce rated torque.
• Drive repeatedly resets during low-voltage conditions.
• Alarm clears after restoring the correct input voltage.

Recommended Troubleshooting Sequence

1. Turn OFF the power supply.
2. Measure the incoming supply voltage.
3. Verify that the supply voltage matches the drive specification.
4. Check the main power switch.
5. Inspect input fuses and circuit breakers.
6. Verify power wiring according to the wiring manual.
7. Tighten all power terminals.
8. Inspect power cables for damage.
9. Check for excessive voltage drop under load.
10. Verify the correct power system is being used.
11. Restore the proper supply voltage.
12. Restart the servo drive.
13. Verify normal operation.
14. Monitor the DC bus voltage.
15. Contact Delta technical support if the alarm persists.

Under Voltage Check Table

Check Point	Action
Incoming supply voltage	Measure and verify within specification
Power wiring	Confirm correct wiring
Main power switch	Verify ON position
Input fuse/circuit breaker	Inspect for operation
Power terminals	Tighten loose connections
Power cables	Inspect for damage
Voltage drop	Measure under load
Power system	Verify correct input voltage and phase configuration
DC bus voltage	Confirm normal charging
Servo operation	Restart and verify normal operation
Delta technical support	Contact if the alarm remains after inspection

Preventive Maintenance Tips

• Periodically verify the incoming supply voltage.
• Inspect power wiring and terminals during scheduled maintenance.
• Tighten input power connections to prevent voltage drops.
• Replace damaged power cables immediately.
• Use properly sized cables to minimize voltage loss.
• Inspect input protection devices regularly.
• Ensure the correct power system is used during installation.
• Protect the servo drive from unstable power supplies.
• Maintain clean and secure electrical connections.
• Record recurring AL003 alarms to assist long-term diagnostics.

Proper verification of the incoming power supply, main circuit wiring, power switch, input protection devices, and power cable connections, along with ensuring that the correct supply voltage is applied to the servo drive, will help prevent recurring AL003 Under Voltage faults in Delta ASDA-B2 servo drives, ensuring stable DC bus voltage, reliable servo performance, and dependable long-term operation of the servo system.