SV0441 Current Offset Error fault in Fanuc drive

SV0441 Current Offset Error fault in Fanuc drive

Description

The servo drive uses current sensors (Hall Effect sensors or Shunt resistors) to measure how much electricity goes to the motor phases (U and V). When the drive is idle (no torque commanded), the current reading should be exactly zero. However, due to component aging and temperature drift, the reading might drift slightly. The drive performs a check upon startup. If the current sensor reports current flow when the transistor is actually off, SV0441 is generated. It essentially means "I am reading current where there should be none."

Cause

This is almost exclusively an internal amplifier control circuit issue.

• A/D Converter Failure: The Analog-to-Digital converter on the control PCB is failing.
• Current Sensor Drift: The physical current sensor inside the drive has become magnetized or damaged.
• Noise: Extreme electrical noise on the ground line can sometimes trick the sensor during the initialization check.

Solution

There are very few external fixes for this.

1. One-Time Reset: Sometimes, simply powering cycling the machine allows the temperature to stabilize, and the offset falls back within acceptable range.
2. Check Grounding: Ensure the drive ground wire is tight. Bad grounding introduces DC offsets.
3. Replace Control Board: If the drive is modular (control card separates from power section), you can try swapping the control card. However, often the current sensors are in the power section, necessitating a full drive replacement.