SV0456 Deceleration Power Error fault in Fanuc drive

SV0456 Deceleration Power Error fault in Fanuc drive

Description

SV0456 is a confusing alarm often mistaken for a standard overload. It occurs specifically when the axis is decelerating. The CNC calculates the expected energy that should be returning to the drive system during braking. If the measured DC Link voltage does not rise as expected, or drops unexpectedly during braking, SV0456 is triggered. It implies a mismatch between the kinetic energy of the motor and the electrical energy seen by the drive.

Cause

• DC Link Connection: The most common cause is a loose connection on the DC bus bars between the PSM and the Servo Amp.
• Capacitor Failure: The DC link capacitors inside the drive have dried out and lost their ability to store energy.
• Parameter: Incorrect setting of the motor inertia parameter. If the control thinks the motor is heavy but it's light, the calculation fails.

Solution

1. Torque Bus Bars: Tighten all screws on the DC Link (top of drives).
2. Check PSM Status: Ensure the Power Supply Module isn't showing an error code.
3. Replace Drive: If the wiring is solid, the internal capacitor bank of the servo amplifier is likely degraded.