earth fault 2 a45 danfoss
In Danfoss VFD, Alarm 45 (Earth Fault 2) is a critical safety trip. While Alarm 14 is a general ground fault that can happen at any time, Alarm 45 specifically occurs during the start-up sequence (when the drive is performing a pre-start check of the motor circuits).
It indicates that a leakage current is flowing from the output phases to the ground, usually due to a breakdown in insulation in the motor or the cabling.
Primary Causes
Insulation Breakdown: The most common cause is moisture or heat damage in the motor windings or the motor power cable.
Moisture in Terminal Box: Water or heavy condensation inside the motor’s electrical junction box.
Cable Damage: A nicked or crushed motor cable where a conductor is touching the conduit or earth.
Current Sensor Offset: Over time, the internal sensors can develop an "offset" (drift), making the drive think there is a leak when there isn't.
Troubleshooting Steps
1. Megger the Motor and Cable
The most effective way to find a real ground fault is using an insulation resistance tester (Megger).
Isolate the Drive: Disconnect the motor cables from the VFD terminals (U, V, W). Never Megger into the drive itself, as you will destroy the power electronics.
Test Phases to Ground: Test each lead (U-Gnd, V-Gnd, W-Gnd). A healthy motor and cable should typically read well above 500 MΩ. If it is below 2 MΩ, you have a confirmed fault.
2. Test the Drive "Open"
To rule out an internal drive failure:
With the motor cables still disconnected, try to start the drive.
If the drive stays in "Running" mode (or gives a "Missing Motor Phase" alarm instead of Alarm 45), the drive is healthy, and the fault is definitely in your cable or motor.
If Alarm 45 returns even with no motor connected, the internal current sensors or the power card have failed.
3. Perform a Manual Initialization (Current Sensor Reset)
If the motor tests fine, the sensors might just need recalibration.
Power off the drive.
Hold [Status], [Main Menu], and [OK] while powering the drive back on.
This resets all parameters to factory defaults and forces the drive to recalibrate its zero-current offsets.
Note: You will need to re-enter your motor nameplate data after this.
4. Check for Moisture
If the system has been sitting idle in a damp environment, run the "Motor Preheat" function if available, or use a space heater to dry out the motor junction box and windings.
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