F0006 DC UNDER VOLTAGE Fault in ABB ACS550 Drive VFD

F0006 – DC UNDER VOLTAGE in the ABB ACS550 Drive VFD indicates that the intermediate DC bus voltage has fallen below the minimum operating level. When the DC link voltage is insufficient, the drive cannot maintain proper inverter operation and trips to protect the power electronics and motor.

This fault is usually caused by a problem with the incoming AC power supply rather than the drive itself.

Possible Causes

• Missing phase in the input power supply.
• Blown input fuse.
• Undervoltage on the mains supply.
• Loose or damaged input power connections.
• Input power supply imbalance.
• Faulty circuit breaker or contactor.
• Power interruption or voltage dip.
• Excessive voltage drop due to undersized cables.
• Internal rectifier or DC bus fault (less common).

Solutions

1. Check for and correct a missing phase in the input power supply.
2. Inspect and replace any blown input fuses.
3. Verify that the mains supply voltage is within the drive's specified operating range.
4. Check all input power cable connections and tighten any loose terminals.
5. Measure the three-phase input voltage and confirm that it is balanced.
6. Inspect the input contactor and circuit breaker for proper operation.
7. Restore stable input power before resetting the fault.
8. If the power supply is normal and the fault persists, inspect the drive's rectifier and DC bus circuitry.

Additional Information

The ABB ACS550 converts the incoming AC supply into a DC voltage in the intermediate circuit (DC bus). If this DC voltage drops below the minimum allowable level, the drive generates F0006 – DC UNDER VOLTAGE and disables the inverter output.

Common causes include:

• Loss of one input phase.
• Low mains voltage.
• Blown fuse.
• Loose input wiring.
• Power supply disturbances.

In rare cases, a defective rectifier or DC bus component inside the drive may also cause this fault.

Common Symptoms

• Drive displays F0006 – DC UNDER VOLTAGE.
• Motor stops unexpectedly.
• Drive will not start.
• Fault occurs during power dips.
• Low DC bus voltage reading.
• Repeated undervoltage trips.
• Production interruptions due to unstable power.

Recommended Troubleshooting Sequence

1. Verify that the displayed fault is F0006 – DC UNDER VOLTAGE.
2. Disconnect power and follow lockout/tagout procedures.
3. Check that all three input phases are present.
4. Inspect the input fuses and replace any that are blown.
5. Measure the incoming line voltage and verify it is within specification.
6. Check for loose or damaged input power connections.
7. Inspect the circuit breaker and input contactor.
8. Restore power and reset the fault.
9. If the fault persists with a normal power supply, inspect the drive's rectifier and DC bus components.
10. Confirm normal drive operation after repair.

F0006 DC UNDER VOLTAGE Check Table

Check Point	Action
Input power phases	Verify all three phases are present
Input fuses	Replace if blown
Mains voltage	Measure and verify within specification
Power connections	Tighten and inspect for damage
Voltage balance	Check for supply imbalance
Circuit breaker/Contactor	Verify correct operation
DC bus	Inspect if the fault persists
Drive operation	Confirm normal startup after repair

Preventive Maintenance Tips

• Periodically inspect and tighten input power terminals.
• Check input fuses during routine maintenance.
• Monitor the incoming power supply for voltage dips and imbalance.
• Maintain circuit breakers and contactors in good condition.
• Use appropriately sized power cables to minimize voltage drop.
• Protect the drive from unstable utility power where possible.
• Record recurring F0006 faults to identify developing supply problems.
• Follow ABB preventive maintenance recommendations for the ACS550 Drive VFD.

Proper inspection of the incoming three-phase supply, input fuses, mains voltage, power wiring, and DC bus will help prevent recurring F0006 – DC UNDER VOLTAGE faults in ABB ACS550 Drive VFDs, ensuring reliable operation and protecting the drive from low-voltage power supply conditions.