Get Started Free

VFD trips on overcurrent at start

Technical review pending. This guide is based on the cited manufacturer documentation; check it against the manual for your exact model and firmware before acting.

A drive that trips on overcurrent the moment it receives a run command, before the motor has really accelerated, is usually telling you about the motor circuit or the start settings, not the ramp. A shorted or grounded cable or winding, too much boost or DC brake current, a brake that has not released, a motor still coasting, or motor data that does not match the motor are the usual causes. A trip partway through the ramp is a different symptom (trips on acceleration) and points to ramp time and inertia.

Diagnose this with AI

Upload a photo of the alarm screen, the fault history or a data export. InduQT compares the evidence and suggests the next useful checks.

Try Free Drive Diagnostic

Where it shows up

Likely causes and how to tell them apart

1Shorted or grounded motor cable or winding

Points to it
Trips instantly every time, even with the load uncoupled; ground-fault codes appear in the history; worse after washdown.
Check
Lock out, disconnect the motor leads at the drive, then megger cable and motor phase-to-phase and phase-to-ground separately.

2Starting into a motor that is still turning

Points to it
Trips only on restarts of fans or high-inertia loads that freewheel.
Check
Enable the drive’s flying start or speed search (G120 p1200, Yaskawa b3-01), or start only after the motor stops.

3Boost, torque compensation or DC brake current set too high

Points to it
Trips at start in V/f mode with little load; settings changed recently.
Check
Check boost and DC brake settings (PowerFlex 525 A530 and A435, Yaskawa E1 V/f pattern and C4-01).

4Mechanical bind or brake not released

Points to it
Motor shaft does not move before the trip; brake coil voltage absent.
Check
Verify the brake releases on the run command and the machine turns freely by hand with power isolated.

5Wrong motor data or connection

Points to it
Trips after a motor or drive swap; star/delta or nameplate data mismatched.
Check
Compare motor data in the drive with the nameplate, check the motor connection, and repeat autotune or motor identification if the manual calls for it.

6Contactor switching between drive and motor

Points to it
An output contactor closes after the drive has already started outputting.
Check
Change the sequence so the contactor closes before the run command and opens after the output stops.

Diagnostic sequence

  1. Capture before resettingPhotograph the code and read the fault log: current and DC bus voltage at the trip, frequency at the trip (near 0 Hz confirms a start trip).
  2. Confirm the timingInstant trip at start: motor circuit, start settings or brake. Partway through the ramp: ramp time and inertia (see trips on acceleration).
  3. Uncouple if you canIf it still trips with the load uncoupled, the problem is electrical (cable, motor, settings), not mechanical.
  4. Test insulation safelyLock out, wait for DC bus discharge per the manual, disconnect the motor leads and megger cable and motor separately.
  5. Review start settingsBoost, DC brake, flying start/speed search, motor data. Change one setting at a time.

Evidence to collect

Work on fuel trains, burners, pressure vessels and electrical equipment must be done by qualified personnel following the manufacturer’s documentation and local codes. Never bypass a safety device or interlock.

Related