LvS/LuS Low-voltage at Stop Fault in Delta C2000 Drive

LvS/LuS – Low-voltage at Stop in the Delta C2000 AC Drive indicates that the DC bus voltage has fallen below the threshold set by Parameter Pr.06-00 while the drive is in the stopped state. In some cases, the fault may also indicate a hardware failure in the DC bus voltage detection circuit.

LvS/LuS Low-voltage at Stop Fault in Delta C2000 Drive


This fault usually results from an unstable or insufficient input power supply, although incorrect drive selection or internal hardware faults can also cause it.

Meaning

  • DC bus voltage is lower than the value set in Parameter Pr.06-00 while the drive is stopped.
  • Possible hardware failure in the DC bus voltage detection circuit.

Possible Causes

  • Power supply interruption (power-off).
  • Incorrect drive model or power specification.
  • Input power voltage fluctuation or undervoltage.
  • Large-capacity motor causing excessive voltage drop during startup.
  • Insufficient power supply capacity.
  • DC bus voltage instability.
  • Hardware failure in the voltage detection circuit.
  • Incorrect input voltage for the selected drive.

Solutions

1. Power-off

  • Improve the power supply condition.

2. Incorrect Drive Model

  • Check that the power supply specification matches the drive rating.

3. Power Voltage Changes

  • Adjust the input voltage so that it remains within the drive's specified operating range.
  • Cycle the power after correcting the supply.
  • If the LvS/LuS fault remains after restoring correct input voltage, the drive may require repair.

4. Starting a Large-Capacity Motor

  • Check the power system.
  • Increase the capacity of the power supply equipment if necessary.

5. DC Bus

  • Install DC reactor(s) to improve DC bus stability.

Additional Information

The Delta C2000 continuously monitors the DC bus voltage. If the voltage drops below the level defined by Pr.06-00 while the drive is stopped, the drive generates LvS/LuS – Low-voltage at Stop.

Typical causes include:

  • Low incoming supply voltage.
  • Power interruptions.
  • Incorrect drive selection.
  • Weak power distribution system.
  • Faulty DC bus voltage sensing circuit.

If the power supply has been verified and the fault still occurs immediately after power-up, the voltage detection circuit inside the drive may require repair.

Common Symptoms

  • Drive displays LvS/LuS – Low-voltage at Stop.
  • Drive cannot start.
  • Fault appears immediately after power-up.
  • Low DC bus voltage reading.
  • Repeated undervoltage faults.
  • Drive remains in fault state after reset.
  • Production stops due to unstable power.

Recommended Troubleshooting Sequence

  1. Verify that the displayed fault is LvS/LuS.
  2. Disconnect power and follow lockout/tagout procedures.
  3. Measure the incoming power supply voltage.
  4. Verify that the drive model matches the available supply voltage.
  5. Check for voltage fluctuations or power interruptions.
  6. Inspect the power distribution system if a large motor is connected.
  7. Install a DC reactor if recommended for the application.
  8. Cycle power after correcting the supply conditions.
  9. If the fault remains, inspect the drive's DC bus voltage detection hardware.
  10. Repair or replace the drive if a hardware fault is confirmed.

LvS/LuS Low-voltage at Stop Check Table

Check PointAction
Power supplyImprove power quality
Drive modelVerify correct voltage specification
Input voltageConfirm within rated range
Power systemCheck for voltage drop during startup
Large motorIncrease supply capacity if required
DC busInstall DC reactor(s) if recommended
Voltage detection circuitInspect if the fault persists
Drive operationVerify normal startup after repair

Preventive Maintenance Tips

  • Periodically monitor the incoming supply voltage.
  • Ensure the selected drive matches the available power supply.
  • Inspect input power connections regularly.
  • Maintain a stable power distribution system.
  • Install DC reactors where recommended by Delta.
  • Tighten all input power terminals during routine maintenance.
  • Record recurring LvS/LuS faults to identify developing power quality issues.
  • Replace damaged power cables or protective devices promptly.
  • Verify supply capacity before connecting large motors.
  • Follow Delta preventive maintenance recommendations for the C2000 Drive.

Proper inspection of the power supply, drive model selection, input voltage, power system capacity, DC bus stability, and voltage detection circuit will help prevent recurring LvS/LuS – Low-voltage at Stop faults in Delta C2000 drives, ensuring reliable operation and protecting the drive from undervoltage conditions.

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