WEG CFW500 fault F0070: Overcurrent/short-circuit
Overcurrent or short circuit on the output, the DC link or the braking resistor. The protection acts in hardware and cuts the output PWM pulses instantly; it corresponds to an overcurrent between output phases. The trip level depends on the power module and is well above the inverter’s rated current (P0295).
Diagnose this with AI
Try Free Drive Diagnostic Upload a keypad photo, the fault history or a parameter export from your WEG CFW500. InduQT compares the evidence and suggests the next useful checks.
When it happens
- At start or during acceleration with too short a ramp
- At start with the motor already spinning and Flying Start off
- Immediately at start when a motor phase, cable or braking resistor cable is shorted
Likely causes and checks
1Short circuit between two motor phases
- Points to it
- Trips instantly at start, even with no load.
- Check
- With the motor disconnected from the inverter, check the motor and motor cable phase to phase.
2Short circuit in the braking resistor cables
- Points to it
- A braking resistor is fitted; trips when braking or at power-up of the output.
- Check
- Inspect the braking resistor and its connecting cables.
3IGBT module short-circuited or damaged
- Points to it
- Trips immediately even with the motor disconnected.
- Check
- The power module is inside the inverter; refer to WEG service.
4Start with too short an acceleration ramp
- Points to it
- Trips partway through the ramp; fewer trips with a longer ramp or lighter load.
- Check
- Check P0100 and the current limitation settings P0135 and P0150.
5Start with the motor spinning and Flying Start off
- Points to it
- Trips when starting a fan or load that is still turning.
- Check
- Check P0320 (Flying Start) for loads that may still be turning at start.
Telling it apart
- An instant trip at start points to a short in the motor, its cable, the braking resistor cables or the IGBTs; a trip partway through the ramp points to ramp time and load.
- F0070 is an overcurrent between output phases; F0074 is an overcurrent from a phase to ground. Repeated F0070 and F0074 together point to cable or motor insulation.
- In V/f and VVW, current limitation (P0135 with P0150) holds or reduces the ramp to prevent F0070; check whether it is set before lengthening ramps.
Relevant parameters
| Parameter | Name | Why it matters |
|---|---|---|
| P0100 | Acceleration time | Too short a ramp is a listed cause. |
| P0135 | Maximum output current (V/f, VVW) | Current limitation level; holding or reducing the ramp at this level prevents F0070. |
| P0150 | Type of DC link and current regulator (V/f, VVW) | Selects Ramp Hold or Decelerate Ramp for current limitation. |
| P0320 | Flying Start / Ride-Through | Flying Start lets the inverter start a motor that is already spinning. |
| P0340 | Auto-reset time | Can reset faults automatically; only enable once the cause is understood. |
Evidence to collect
- Fault history P0050–P0055, especially P0051 (current) and P0053 (frequency) at the trip
- Acceleration time P0100 and current limit P0135
- Whether the load can still be turning at start, and P0320
- Motor and cable checks with the motor disconnected
- Whether a braking resistor is fitted
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