Why Does the Drive Throw an Earth Fault Alarm?
If you see an "Earth Fault" or "Ground Fault" warning on your CNC screen or inverter, electrical current is escaping to the motor's metal housing instead of traveling through the windings. This creates a lethal shock hazard, and drives instantly shut down.
Mechanical and Electrical Causes
- Scorched Insulation: Overheating melts the insulating paper or wire varnish. Bare copper touches the iron core.
- Fluid Ingress: Water or coolant entering the motor creates a conductive bridge between the windings and the housing.
- Crushed Cables: The power cable's outer armor wears out, and phase wires touch the machine chassis.
Megger Testing and Winding Curing
We use a Megger (1000V DC Insulation) Tester in the Code Elektronik Lab to pinpoint the fault. If the winding insulation has collapsed, the motor is rewound using Class-H insulating materials, impregnated with resin via VPI, and baked in industrial ovens to eliminate the earth fault entirely.