VFD / Drive Troubleshooting: Causes & Fixes

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Problems on this page:

Overvoltage (DC bus) trip Overcurrent / overload trip Drive overtemperature Ground or earth fault trip Motor will not reach set speed Nuisance tripping or random faults Output phase loss or motor runs rough Drive will not start on a run command

Overvoltage (DC bus) trip

Hits OEE: Availability

Symptoms: Drive trips on overvoltage, usually during deceleration or stopping.

Deceleration ramp too fast (regeneration)

Extend the decel time, or add a brake resistor/unit to absorb regen energy.

Supply voltage spikes / high line

Check incoming voltage; add line reactor if supply is unstable.

Overhauling load

Size dynamic braking for the load.

Prevention: Correct decel ramps, brake resistor sizing, supply quality checks.

Overcurrent / overload trip

Hits OEE: Availability

Symptoms: Drive trips on overcurrent or overload, often at start or under load.

Mechanical overload or jam

Inspect the driven load for binding; clear it.

Acceleration too fast

Extend the accel ramp; check torque-boost settings.

Motor or cable fault

Megger the motor and cable; check connections.

Wrong motor parameters

Re-enter nameplate data; run drive auto-tune.

Prevention: Auto-tune on commissioning, correct ramps, load checks.

Drive overtemperature

Hits OEE: Availability

Symptoms: Drive trips or derates on high heatsink temperature.

Blocked cooling / dirty heatsink

Clean the heatsink and vents; clear cabinet airflow.

Failed cooling fan

Replace the drive/cabinet cooling fan.

High cabinet ambient

Improve enclosure cooling or ventilation.

Prevention: Cabinet filter changes, fan checks, enclosure cooling.

Ground or earth fault trip

Hits OEE: Availability

Symptoms: Drive trips on ground fault at start or run and will not stay running.

Motor or cable insulation breakdown

Megger the motor and cable; repair or replace the faulted item.

Moisture or contamination

Dry and clean terminations; seal cable entries.

Damaged output cable

Inspect for chafing or crush; replace the cable.

Prevention: Insulation testing, sealed terminations, cable protection.

Motor will not reach set speed

Hits OEE: Performance

Symptoms: Output stuck below setpoint, current limiting, slow acceleration.

Current or torque limit reached

Check the load and mechanical drag; review the limit settings.

Accel ramp or speed reference wrong

Verify the speed-reference source and the ramp times.

Undersized drive or low voltage

Confirm drive sizing and the incoming supply voltage.

Prevention: Correct sizing, parameter review, load and supply checks.

Nuisance tripping or random faults

Hits OEE: Availability

Symptoms: Intermittent unexplained trips that clear on reset, with no clear pattern.

Electrical noise or EMI

Use screened cable, proper earthing and separation from signal wiring.

Loose power or control terminations

Torque-check all terminals; inspect for hot joints.

Supply disturbance

Check for sags and spikes; add a line reactor or filter if needed.

Prevention: EMC wiring practice, terminal checks, supply-quality monitoring.

Output phase loss or motor runs rough

Hits OEE: Performance

Symptoms: Rough running, vibration, output phase-loss fault, torque ripple.

Loose output connection

Torque-check output terminals and motor connections.

Output cable or motor winding fault

Megger the cable and motor; repair or replace.

Parameter or tuning issue

Check motor data and tuning/autotune.

Prevention: Termination checks, insulation testing, correct motor parameters.

Drive will not start on a run command

Hits OEE: Availability

Symptoms: Run is given but the drive stays stopped, sometimes with no fault shown.

Enable or safe torque off input not made

Check the enable and safe torque off inputs and the safety circuit that feeds them.

Drive set to the wrong control source

Check where the drive takes its run command and speed reference from (keypad, terminals or network).

Speed reference at zero

Check the analog or network speed reference.

Drive left in local or hand mode

Return the drive to remote or auto mode.

Prevention: Parameter backups and a commissioning checklist for every drive.

Guidance only. Always follow lockout/tagout and your site's safe-work procedures, and verify against OEM manuals before acting.

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Related equipment guides: servo drive · electric motor · PLC controls · transformer · switchgear · motor control centre · HMI panel · soft starter

Stop the same fault coming back

Recurring VFD / drive stops usually trace to a cause you cannot see by hand. The partner we recommend is Fabrico: it tracks OEE and downtime live from PLCs, IoT sensors or AI cameras; where cameras are fitted, the video of a stop sits next to its machine data so the cause can be reviewed; and a technician opens the work order from the stop in the same system. Data is hosted in the AWS EU region, and Fabrico and the company behind it hold ISO/IEC 27001, ISO/IEC 20000-1 and ISO 9001.

Book a Fabrico demo

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Methods that cut recurring stops: the six big losses · root cause analysis · preventive vs predictive maintenance · TPM · SMED & changeover