VFD / drive Troubleshooting

Symptoms: Drive trips on overvoltage, usually during deceleration or stopping. Likely causes: Deceleration ramp too fast (regeneration); Supply voltage spikes / high line; Overhauling load. Fixes: Extend the decel time, or add a brake resistor/unit to absorb regen energy. Check incoming voltage; add line reactor if supply is unstable. Size dynamic braking for the load. Prevention: Correct decel ramps, brake resistor sizing, supply quality checks.

Symptoms: Drive trips on overcurrent or overload, often at start or under load. Likely causes: Mechanical overload or jam; Acceleration too fast; Motor or cable fault; Wrong motor parameters. Fixes: Inspect the driven load for binding; clear it. Extend the accel ramp; check torque-boost settings. Megger the motor and cable; check connections. Re-enter nameplate data; run drive auto-tune. Prevention: Auto-tune on commissioning, correct ramps, load checks.

Symptoms: Drive trips or derates on high heatsink temperature. Likely causes: Blocked cooling / dirty heatsink; Failed cooling fan; High cabinet ambient. Fixes: Clean the heatsink and vents; clear cabinet airflow. Replace the drive/cabinet cooling fan. Improve enclosure cooling or ventilation. Prevention: Cabinet filter changes, fan checks, enclosure cooling.

Symptoms: Drive trips on ground fault at start or run and will not stay running. Likely causes: Motor or cable insulation breakdown; Moisture or contamination; Damaged output cable. Fixes: Megger the motor and cable; repair or replace the faulted item. Dry and clean terminations; seal cable entries. Inspect for chafing or crush; replace the cable. Prevention: Insulation testing, sealed terminations, cable protection.

Symptoms: Output stuck below setpoint, current limiting, slow acceleration. Likely causes: Current or torque limit reached; Accel ramp or speed reference wrong; Undersized drive or low voltage. Fixes: Check the load and mechanical drag; review the limit settings. Verify the speed-reference source and the ramp times. Confirm drive sizing and the incoming supply voltage. Prevention: Correct sizing, parameter review, load and supply checks.

Symptoms: Intermittent unexplained trips that clear on reset, with no clear pattern. Likely causes: Electrical noise or EMI; Loose power or control terminations; Supply disturbance. Fixes: Use screened cable, proper earthing and separation from signal wiring. Torque-check all terminals; inspect for hot joints. Check for sags and spikes; add a line reactor or filter if needed. Prevention: EMC wiring practice, terminal checks, supply-quality monitoring.

Symptoms: Rough running, vibration, output phase-loss fault, torque ripple. Likely causes: Loose output connection; Output cable or motor winding fault; Parameter or tuning issue. Fixes: Torque-check output terminals and motor connections. Megger the cable and motor; repair or replace. Check motor data and tuning/autotune. Prevention: Termination checks, insulation testing, correct motor parameters.