Inverter fault - The VLT® power section is defective.

Overvoltage - The voltage of the VLT® frequency converter’s intermediate circuit (DC-voltage) is too high. Possible reasons: line voltage too high, transients on the line voltage, or re- generative motor operation.
Note: When the VLT® frequency converter is stopped, repeated transients are charging the intermediate circuit, as it supplies no power to the motor.

• If the fault indication is given when the speed is reduced, you can increase the ramp-down time. If this is not possible, the application may require a VLT® frequency converter with brake. If the fault indication is given in other situations, the problem will be due to the mains supply.

Undervoltage - The voltage of the VLT® frequency converter’s intermediate circuit (DC-voltage) is too low. Possible reasons: line voltage too low or defect in the VLT® frequency converter’s charging circuit/rectifier.

• Check whether the line voltage is OK.

Overcurrent - The peak current limit of the inverter has been reached. This may be due to a short- circuit in the output of the VLT® frequency converter.

• Check the motor and the motor cable for ground failure.

Ground fault - Ground failure on the VLT® frequency converter output. Another reason might be that the motor cable is too long.

• Consult the data sheets for permitted cable length.
• Check the motor and the motor cable for earth leakage.

Over-temperature - The temperature inside the VLT® frequency converter is too high. Possible reasons: the ambient temperature is too high (max. 40/45 °C), the VLT® frequency converter’s cooling ribs are covered, or the VLT® frequency converter's fan is defective.

• Reduce the ambient temperature by increasing the ventilation. Uncover/clean the cooling ribs. Replace the fan.

Overload - The electronic VLT® protection is active. This means that the motor has consumed more than 105% of rated VLT® frequency converter current for too long.

• Reduce the motor load. If this is not possible the application may require a larger VLT® frequency converter.

Motor trip - The electronic motor protection is active. This means that the current consumed by the motor at low speed has been too high for too long.

• The motor has been loaded excessively at low speed. If the load cannot be changed, you must exchange the motor for a bigger one, or provide extra cooling of the existing motor. If so, the electronic motor protection can be de-activated in parameter 315.