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Why Does a Home Lift Stop Immediately? Understanding Low Voltage Faults in VFDs

Variable Frequency Drives (VFDs) are widely used in hydraulic home lifts. They not only convert single-phase 220V power into three-phase 380V power for the hydraulic pump, but also control motor speed for smoother operation.

Recently, one of our customers reported that his home lift stopped immediately after pressing the UP button. The inverter displayed the fault code:

ELUO

The inverter installed in the control cabinet was a SU-600 VFD.

According to the operation manual, ELUO indicates an input under-voltage fault.

Why Low Voltage Causes a Fault

When the input voltage becomes too low, the inverter must draw higher current to maintain output power.

Higher current places additional stress on the DC bus capacitors inside the inverter. Excessive current can shorten capacitor life or even damage internal components.

To protect itself, the inverter automatically stops operating and displays the ELUO fault code.

Why Manual Mode Still Worked

The customer noticed that the lift operated normally in manual mode.

This is because manual operation runs at approximately 25 Hz, requiring less power from the motor.

Lower frequency means:

• Lower motor load

• Lower current demand

• Reduced voltage drop

Therefore, the inverter does not enter under-voltage protection.

Wiring Matters

Low voltage problems are not always caused by the power supply itself.

Small cable sizes, loose terminals, and poor electrical connections can also cause voltage drops.

Always ensure:

• Proper cable sizing

• Tight terminal connections

• Stable input voltage

• Secure breaker connections

Ignoring these details may eventually damage the inverter capacitors or other internal components.

Conclusion

An ELUO fault does not necessarily mean the inverter has failed.

Before replacing the VFD, users should first inspect the incoming voltage, cable size, and wiring conditions.

Proper installation and maintenance can significantly increase the service life of both the inverter and the hydraulic lift system.