SV0458 Current Loop Error fault in Fanuc drive

SV0458 Current Loop Error fault in Fanuc drive

Description

SV0458 is an internal diagnostic alarm of the servo amplifier. The drive's CPU constantly calculates the required current (Torque) using a PI (Proportional-Integral) loop. It compares the calculated request against the actual current output. If the math doesn't add up—meaning the output current is vastly different from what the processor is trying to command—it triggers SV0458. This effectively means the "Brain" of the drive has lost control of the "Muscle" (Transistors).

Cause

• Current Sensor Failure: The Hall effect sensors inside the drive are reporting static or garbage data.
• Parameter Corruption: The motor parameters (inductance/resistance values) loaded in the CNC do not match the actual motor, making the math loop unstable.
• Drive Board Failure: The firing circuit for the IGBTs is dead, so the CPU commands current but nothing happens.

Solution

1. Reload Parameters: If this happened after a data loss, ensure the Motor ID is correct. The drive needs to know the motor's electrical characteristics to calculate the loop.
2. Replace Drive: SV0458 is almost universally a fatal failure of the Servo Amplifier control board or current sensing hardware. It is rarely repairable in the field.