VFD trips on acceleration
A drive that trips while ramping up is almost always reporting overcurrent (or current limit). The motor is drawing more current than the drive allows: because the ramp asks for more torque than the load can take, because the load is stuck, or because of a fault in the motor or its cable.
Diagnose this with AI
Try Free Drive Diagnostic Upload a photo of the alarm screen, the fault history or a data export. InduQT compares the evidence and suggests the next useful checks.
Where it shows up
- An overcurrent or current-limit fault during start or speed increase
- Trips that disappear when the acceleration time is lengthened
Likely causes and how to tell them apart
1Acceleration ramp too short for the inertia
- Points to it
- Trips only during fast starts; fans and centrifuges are typical.
- Check
- Compare the acceleration time setting with the load’s inertia; trial a longer ramp and watch peak current.
2Mechanical load or brake not released
- Points to it
- Trips immediately at start; motor barely turns.
- Check
- Confirm the brake releases and the driven machine turns freely.
3Motor data or control mode wrong
- Points to it
- Trips after a drive replacement or parameter change.
- Check
- Check motor nameplate data in the drive and that the motor identification run was done if the drive requires it.
4Motor or cable insulation fault
- Points to it
- Instant trip at start even unloaded; may alternate with ground-fault trips.
- Check
- Insulation-test the motor and cable with the motor disconnected from the drive.
Diagnostic sequence
- Read the fault and its logNote the fault code and, if the drive stores them, the current, frequency and DC voltage at the trip.
- When in the ramp?Instantly at start points to motor, cable or brake; partway through the ramp points to ramp time or load inertia.
- Compare with the loadWas the machine heavily loaded, cold or recently serviced?
- Change one settingIf mechanics and wiring are healthy, lengthen the ramp in steps and compare peak current.
Evidence to collect
- Keypad photo of the fault
- Drive model and firmware
- Fault log values at the trip
- Acceleration time and current limit settings
- Description of the driven load
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