Danfoss VLT AutomationDrive FC 302 fault A14: Earth (Ground) Fault
Alarm 14 on a Danfoss VLT FC 302 is Earth (Ground) Fault: current is flowing from an output phase to ground, in the cable between drive and motor or in the motor itself. The drive compares the current going out to the motor with the current coming back and trips when the difference is too large.
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
- At start or first run after the machine stood idle or was washed down
- While running, especially hot or under vibration
- After drive service such as a power card change
Likely causes and checks
1Motor cable insulation damage
- Points to it
- Cable runs through wet conduit, flexes with the machine, or was recently disturbed; trip may come at any speed.
- Check
- Lock out, wait the nameplate discharge time, disconnect the cable at the drive and at the motor, and megger each conductor to ground.
2Motor winding insulation breakdown
- Points to it
- Cable tests good; motor is old, has overheated, or runs in a wet or dusty area.
- Check
- Megger the motor windings to ground with the motor disconnected from the drive (Danfoss lists a megohmmeter test of motor and cables).
3Moisture or contamination in the motor terminal box
- Points to it
- Trips on the first start after idle time or wash-down, then may clear once warm.
- Check
- Open the terminal box (locked out) and look for water, tracking or debris; retest insulation after drying.
4Current sensor offset in the drive
- Points to it
- Motor and cable test good; alarm began after the power card was changed.
- Check
- Danfoss: reset the individual offset in the 3 current sensors by a manual initialization or a complete AMA.
Telling it apart
- Alarm 14 is current to ground; Alarm 16 Short Circuit is phase-to-phase short in the motor or wiring; Alarm 13 is peak overcurrent. A ground fault can also show as A13 if the leakage is large.
- Alarm 45 Earth Fault 2 is a separate ground-fault alarm; Danfoss lists grounding, loose connections, wire size and cable leakage currents as its checks.
- Timing: first start after idle or wash-down points to moisture; trips that follow a power card change with healthy insulation point to sensor offset.
Relevant parameters
| Parameter | Name | Why it matters |
|---|---|---|
| 1-29 | Automatic Motor Adaptation (AMA) | A complete AMA resets current sensor offsets (Danfoss, most relevant after a power card change). |
Evidence to collect
- Alarm log entry for A14 with time
- Megger readings for each motor cable conductor and the motor, taken with both disconnected from the drive
- Recent wash-down, rain or condensation
- Recent drive service (power card change)
- Cable length and routing
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