Common LS inverter faults: symptoms and checks

Common LS drive fault codes are listed below. Check the exact drive model and manufacturer manual. Electrical inspection, disconnection and maintenance must be performed by qualified personnel after isolation and confirmation of safe conditions under the equipment instructions.

OCt — Overcurrent

(Overcurrent): a commonly encountered trip. Check the following possible causes.

• A seized motor shaft or damaged bearings.
• An excessive load causing a sudden rise in current.
• Damaged wiring or a lost phase between the drive and motor. Pay particular attention to systems using slip rings or quick connectors; confirm the actual fault code against the model manual.

OLt — Overload

(Overload)

• A motor or load that exceeds the drive's rating.
• Check motor cable length against the manufacturer's permitted limits and installation requirements.

FAN — Cooling-fan fault

(Cooling-fan fault)

• A failed cooling fan or damaged fan-supply wiring. Exposed wiring may be damaged by insects.

OHt — Overheating

(Overheating)

• The heat-sink temperature exceeds its permitted limit. This differs from a fan-fault alarm: the fan may still operate, but a hot installation environment or inadequate ventilation can prevent effective cooling.

OUt — Overvoltage

(Overvoltage): the drive's DC-link voltage exceeds the permitted value. Also assess mechanical load conditions during diagnosis.

• An excessively slack drive chain or belt.
• Uneven or eccentric loads, such as rice-screening machinery or rotary tables. Braking arrangements, including a suitable braking resistor where required, must be selected according to the drive manufacturer's instructions and the actual regenerative load.

rErr — Keypad communication fault

(Communication fault)

• A poor connection in the communication cable between the keypad and drive. Connections may have been affected during transport or installation and should be inspected by a qualified technician after safe isolation.

HWt — Hardware fault

(Hardware fault): refer the drive to the supplier or an authorised service centre. This is beyond routine operator troubleshooting.

These are examples of common faults; the correct diagnosis depends on the drive model, fault code and operating conditions.

LS Electric — iG5A manual