Danfoss FC302 VFD ALARM 57 — What It Means
ALARM 57 on a Danfoss VLT FC 302 is labeled “AMA internal fault.” This means the drive’s Automatic Motor Adaptation (AMA) procedure has encountered an internal error and could not complete. The AMA routine measures motor characteristics to optimize drive performance, and this fault indicates the process failed. Danfoss instructs technicians to restart the AMA and continue retrying until the procedure completes successfully. If the alarm persists after multiple attempts with correct motor data and wiring, the fault likely points to an internal drive hardware problem requiring manufacturer service.
Common Causes
- Incorrect motor nameplate data entered in the drive AMA depends on accurate motor parameters, and mismatched voltage, current, or frequency values will prevent the adaptation from completing.
- Motor wiring errors or loose connections AMA requires a solid electrical path to the motor, so incorrect phase wiring, reversed leads, or poor terminations can trigger the internal fault.
- Motor cable damage or high resistance Damaged insulation, corroded terminals, or undersized cable can interfere with the AMA measurement cycle and cause the procedure to fail.
- Drive control card or power section fault An internal hardware problem in the drive’s control electronics or power stage can prevent AMA from executing properly.
- Incompatible or unsuitable motor for AMA Some motor types or sizes may not work with the AMA routine on the FC 302, causing the procedure to abort with an internal fault.
Step-by-Step Fix
- Check the motor nameplate and verify that all motor parameters entered in the drive (voltage, current, frequency, power, speed) exactly match the motor rating.
- Inspect motor wiring and connections at the drive output terminals and motor terminal box for correct phasing, tight terminations, and absence of damage or corrosion.
- Test motor cable integrity using a megohmmeter to check for insulation breakdown or a multimeter to confirm continuity and balanced phase resistance.
- Restart the AMA procedure from the drive’s parameter menu and allow it to run to completion without interruption.
- Repeat the AMA if the alarm occurs again, ensuring the motor is disconnected from the load and free to spin during the adaptation.
- Review drive firmware version and consult Danfoss documentation to confirm the connected motor type is supported for AMA on your FC 302 model.
- Contact Danfoss service or your supplier if ALARM 57 returns after multiple AMA attempts with verified motor data and wiring, as the fault likely indicates internal drive hardware failure requiring factory-level diagnosis.
Parts Often Needed
| Part | Notes |
|---|---|
| Danfoss FC 302 control card | Amazon | Required if internal control electronics are diagnosed as faulty by Danfoss service after repeated AMA failures. |
| Danfoss FC 302 power card | Amazon | May be needed if the power section is determined to be the source of the AMA internal fault during manufacturer troubleshooting. |
When to Call a Pro
Call a qualified VFD technician or Danfoss-authorized service provider if ALARM 57 persists after you have verified correct motor nameplate data entry, inspected and confirmed proper motor wiring, and retried the AMA procedure at least twice. Repeated AMA internal faults after correct setup indicate a hardware issue inside the drive that requires factory-level diagnostics and potentially control card or power section replacement. Do not attempt to disassemble or repair internal drive components yourself, as this work requires specialized training and will void warranty coverage.