SP9011 (Alarm 11) Spindle DC Link Overvoltage fault in Fanuc drive

SP9011 (Alarm 11) Spindle DC Link Overvoltage fault in Fanuc drive

Description

SP9011 is the Spindle equivalent of the Servo Overvoltage (SV0439). It occurs when the spindle is decelerating from high speed (e.g., 10,000 RPM to 0). The motor acts as a generator. If the regenerative energy cannot be pushed back into the power line (Regen PSM) or dissipated into resistors (Resistor PSM) fast enough, the DC bus voltage spikes. If it hits 800V+, Alarm 11 trips.

Cause

• Input Voltage High: Shop power is running high (e.g., 250VAC).
• Regen Circuit Failure: The PSM's regeneration IGBTs or resistors are failed.
• High Inertia: A very heavy chuck or workpiece is mounted, generating more energy than the system is designed to absorb.

Solution

1. Check Input: Verify AC input is within range (200-220V). Use a transformer if necessary.
2. Increase Decel Time: Extend the deceleration time constant in the parameters. This spreads the energy dump over a longer period, keeping voltage lower.
3. Check Resistors: Measure the external braking resistors for continuity.