What is Fanuc Alarm 438?
One of the most feared errors by operators on Fanuc CNC machines is "Alarm 438: Inv Abnormal Current". This error indicates that the servo drive (amplifier) has detected a much higher current than normal going to the motor and has protected the system.
Why Does It Occur?
- Internal Motor Short Circuit: If coolant or water enters the servo motor, a short circuit occurs between the windings. The drive pushes current, but it leaks to ground, triggering Alarm 438.
- Mechanical Locking: If the relevant axis (X, Y, or Z) guideways are jammed due to lack of lubrication or shattered bearings, the motor struggles to turn and draws excessive current.
- IGBT Module Failure: If the issue isn't the motor or mechanics, the power transistors (IGBT) inside the servo amplifier have blown. The device is short-circuiting internally.
How to Respond?
Repeatedly resetting and powering up the machine when this error occurs can completely burn the drive's motherboard. The Code Elektronik field team detects whether the issue is from the motor, cable, or drive on-site using megger (insulation) tests and provides a guaranteed solution.