Danfoss FC 302 trips A13 during ramp-up, what to check?
My Danfoss FC 302 drive is tripping with an A13 Overcurrent alarm. It happens consistently during the ramp-up phase, especially with heavier loads. What should I check first?
Alarm 13 (Overcurrent) on a Danfoss VLT FC 302 indicates the output current has exceeded the inverter's peak current limit, which is approximately 200% of the drive's rated current. This alarm is typically preceded by a Warning 13 for about 1.5 seconds before the drive trips. The timing of the trip, such as during ramp-up or instantly at start, helps narrow down the potential causes.
Likely causes and checks
1Acceleration too fast for the load inertia
- Points to it
- If the acceleration rate is too high for the connected load, especially with high-inertia loads, the drive will demand excessive current during ramp-up to achieve the set speed, leading to an overcurrent trip.
- Check
- Lengthen the '3-41 Ramp 1 Ramp Up Time' parameter. Compare the peak current shown on the LCP before and after adjusting the ramp time to ensure it stays below the '4-18 Current Limit'.
2Shock load or jammed mechanism
- Points to it
- A sudden increase in load (shock load) or a mechanical obstruction causing the motor to seize can cause an immediate surge in current that exceeds the drive's limit.
- Check
- With power removed and locked out, manually check that the motor shaft and the driven machine turn freely without any binding or jamming.
3Motor data wrong or motor too large for the drive
- Points to it
- Incorrect motor parameters or an oversized motor can lead to the drive miscalculating the required current, causing overcurrent trips, particularly if the drive or motor was recently replaced or parameters were reset.
- Check
- Verify that the motor size matches the drive's specifications and that parameters '1-20' to '1-25' accurately reflect the motor's rating plate. Run the Automatic Motor Adaptation (AMA) function ('1-29') if it hasn't been performed.
4Fast ramp-up after kinetic back-up
- Points to it
- If the drive is configured for kinetic back-up (mains dip ride-through) and experiences a supply dip, a subsequent rapid ramp-up can draw excessive current and trigger an overcurrent alarm.
- Check
- Review parameter '14-10 Mains Failure' settings and check the alarm log times against any plant supply events to see if the trip follows a power dip.
Next check: Given that the trip occurs consistently during ramp-up with heavier loads, the first step should be to lengthen the '3-41 Ramp 1 Ramp Up Time' parameter and monitor the peak current on the LCP.
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