WEG CFW500 trips F0070 instantly at start, even with no load, what to check?
My WEG CFW500 inverter is tripping with an F0070 fault code immediately upon starting, even when the motor is disconnected. What should I investigate first to resolve this?
The F0070 fault on a WEG CFW500 inverter indicates an overcurrent or short circuit on the output, DC link, or braking resistor. An instant trip at start, especially with no load, strongly suggests a short circuit in the motor, its cables, the braking resistor cables, or the inverter's internal power module. This protection acts in hardware to instantly cut the output PWM pulses.
Likely causes and checks
1IGBT module short-circuited or damaged
- Points to it
- If the inverter trips immediately even with the motor disconnected, it points to a potential internal hardware issue within the inverter's power module.
- Check
- The power module is inside the inverter; refer to WEG service for inspection and repair.
2Short circuit between two motor phases
- Points to it
- A short circuit between motor phases can cause an instant trip at start, even with no load connected to the motor shaft.
- Check
- With the motor disconnected from the inverter, check the motor and motor cable phase to phase for continuity or shorts.
3Short circuit in the braking resistor cables
- Points to it
- If a braking resistor is fitted, a short in its cables can cause an F0070 trip when the output is powered up.
- Check
- Inspect the braking resistor and its connecting cables for any signs of damage or short circuits.
Next check: If the issue persists after checking the above, and especially if the trip is instant with the motor disconnected, contacting WEG service for an internal inspection of the inverter's power module is recommended.
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