Danfoss VLT AutomationDrive FC 302 fault A9: Inverter Overload
Alarm 9 on a Danfoss VLT FC 302 is Inverter Overload: the drive has run with more than 100% overload for too long and its electronic thermal inverter protection counter reached 100%. It cannot be reset until the counter falls below 90%.
Diagnose this with AI
Try Free Drive Diagnostic Upload a keypad photo, the fault history or a parameter export from your Danfoss VLT AutomationDrive FC 302. InduQT compares the evidence and suggests the next useful checks.
When it happens
- During long periods at high load
- On repeated heavy starts or duty cycles
- Builds up over minutes rather than tripping instantly
Likely causes and checks
1Load above the drive’s continuous rating
- Points to it
- Trips after running loaded for a while; LCP output current above drive rated current.
- Check
- Compare the output current on the LCP with the drive rated current, and watch the thermal drive load reading rise above its continuous rating.
2Mechanical overload in the driven machine
- Points to it
- Current has crept up over weeks; bearings, gearbox or process load changed.
- Check
- Measure motor current and compare with history; inspect the driven machine.
3Drive reading does not match the real motor current
- Points to it
- LCP current differs from a clamp-meter reading.
- Check
- Compare the LCP output current with the measured motor current (Danfoss check); check motor data 1-20 to 1-25.
4Drive undersized for the duty
- Points to it
- Recently changed application, larger motor, or heavy-duty cycle on a normal-duty rating.
- Check
- Check the drive type code (15-45) against the motor and duty.
Telling it apart
- Alarm 9 protects the drive; Alarm 10 Motor ETR Overtemperature protects the motor. Both are time-based counters, unlike instant Alarm 13 Overcurrent.
- Alarm 9 is listed by Danfoss as warranty-affecting in emergency mode; alternatively 14-61 Function at Inverter Overload can be set to derate.
Relevant parameters
| Parameter | Name | Why it matters |
|---|---|---|
| 14-61 | Function at Inverter Overload | Can be set to [0] Derate per the alarm/warning code list. |
Evidence to collect
- Thermal drive load and output current trend
- Clamp-meter motor current
- Drive rated current (type code) vs motor current
- Duty cycle description
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