An overcurrent fault is the most common reason a VFD trips. On the SHZK 300N it appears as Err02 (acceleration overcurrent), Err03 (deceleration overcurrent) or Err04 (constant-speed overcurrent). The three codes have different triggers, so the first question is always: does it trip while speeding up, slowing down, or at a steady speed? That tells you where to look.
What “overcurrent” actually means
The drive constantly measures output current. If it rises above the hardware protection limit, the drive instantly cuts the IGBT output and displays the Err code to protect both the power module and the motor. This is not a defective drive — it is the drive correctly preventing damage. In most cases an installation, parameter or load problem is forcing too much current.
Tell the codes apart first
- Err02 – during acceleration: accel time too short, no motor tuning, short circuit, or starting a spinning motor.
- Err03 – during deceleration: decel time too short or sudden load change.
- Err04 – at constant speed: load surge, low input voltage, or a mechanical jam.
Step 1 — Rule out a real short or ground fault (do this first)
A genuine short circuit trips almost immediately and any parameter change is unsafe. Check in this order:
- Power off and lock out. Wait for the charge LED to go out (DC bus holds voltage for several minutes).
- Disconnect the motor cables from the U/V/W terminals.
- Megger the motor and cable phase-to-phase and phase-to-ground. A reading below about 5 MΩ indicates damaged insulation or moisture.
- Check the terminal box for loose strands bridging terminals — a very common cause after reconnection.
- Run the drive without the motor. If it still trips, the fault is inside the drive; if it runs clean, the problem is in the cable or motor.
Step 2 — Run motor auto-tuning (the #1 fix on new installs)
In sensorless vector control (P0-01 = 0, the factory default) the drive builds a model of your motor. If you never run auto-tuning, that model is based on generic values, and the very first start can draw high current and trip Err02. This is the single most common cause of overcurrent on a brand-new installation.
- Enter the motor nameplate data in P1-01 to P1-05.
- Set P1-37 = 2 (static tuning) if the load cannot be decoupled, or P1-37 = 1 (rotational tuning) for best accuracy.
- Press RUN and wait until the display returns to standby. Full procedure is in the parameter setup & auto-tuning guide.
Step 3 — Fix it by when the trip happens
| When it trips | Code | Adjustments to make, in order |
|---|---|---|
| While accelerating | Err02 | Increase acceleration time P0-17; run tuning; reduce manual torque boost P0-16 or enable auto-boost; use speed-tracking start (P6-00 = 1) if the motor is already spinning; confirm input voltage. |
| While decelerating | Err03 | Increase deceleration time P0-18; add a braking resistor for high-inertia loads; check for a sudden load drop. |
| At constant speed | Err04 | Look for a load surge or mechanical jam; verify input voltage (low volts = high current); check current limit P2-26; upsize the drive if the load genuinely exceeds its rating. |
Long motor cables need special attention
A long shielded cable to the motor adds capacitance. At every IGBT switch the drive charges that capacitance, creating a brief current spike that can look like a short and trip the drive — or damage the motor bearings. As a rule of thumb, fit an output reactor above roughly 30 m of cable and an output dv/dt or sine filter above 100 m. Lowering carrier frequency (P0-16 group / P0-15) also reduces the spike at the cost of slightly more motor noise.
From our test bench
When we commission a vector-controlled drive on the test line we always rotate-tune it before applying load — every unit, without exception. When a customer reports Err02 on a newly installed drive, roughly eight times out of ten the tuning was skipped or the motor nameplate data was left at default. Run the five checks above in order and the fault will almost always point to one clear cause.
Related Technical Guides
Talk to the engineers who built this drive
Stuck on a fault code, wiring or tuning? Our engineers test every SHZK 300N drive before it ships. Send us your setup and we will reply with the exact fix.