FANUC SP9011 means that the DC link voltage in the main circuit has risen abnormally. The spindle amplifier displays alarm 11, and the common power supply module may simultaneously display alarm 7.
This alarm often occurs while a high-inertia spindle motor is decelerating from high speed. If regenerative braking does not operate correctly when motor power is interrupted, the motor may coast instead of stopping immediately, causing the DC link voltage to rise.
| Alarm location | Display | Meaning |
|---|---|---|
| CNC | SP9011 | DC link overvoltage |
| Spindle amplifier | 11 | DC link overvoltage |
| Common power supply module (PSM) | 7 | Abnormally high DC link voltage |
1. Check the Common Power Supply and Input Voltage
First, check whether the common power supply module also displays alarm 7. Measure the input voltage and confirm that it is stable and within the specified range.
If possible, use suitable measuring equipment to observe power-supply variation, especially while the spindle motor is decelerating. For the applicable FANUC configuration, investigate the power source if the voltage exceeds:
- AC 253 V for a 200 V-class system
- AC 530 V for a 400 V-class system
FANUC specifies that the power-source output impedance is normal when the voltage variation at maximum output is within 7%. If the incoming supply fluctuates significantly, improve the power-supply condition. A voltage stabilizer may be considered when the machine’s main input voltage cannot otherwise be kept stable.
2. Verify the Power Supply Module Capacity
Excessive regenerated power can trigger this alarm when the common power supply module does not have sufficient capacity.
Confirm that the total required capacity of the connected spindle and servo amplifiers is within the maximum output specification of the selected power supply module. Use the applicable FANUC selection manual or contact FANUC to recalculate the power module selection.
If the installed power supply module is undersized, replace it with a correctly rated module.
3. Check Spindle Initialization and Motor-Specific Parameters
Confirm that the spindle initialization parameters are correct. FANUC troubleshooting guidance also includes testing parameter P4672.
If changing P4672 does not resolve the alarm, identify the exact spindle motor model and check its motor-specific parameters against the applicable FANUC AC Spindle Motor Parameter Manual B-65280CM. Reinitialize the spindle motor parameters when required, then test the machine again.
Parameter settings depend on the CNC, spindle motor, spindle amplifier, and software configuration. They should be checked and changed only by qualified personnel using the correct FANUC documentation for the machine.
4. Check for an Abnormal Main-Circuit Power Interruption
If SP9011 occurs after the main circuit is unexpectedly switched off during normal machine operation, inspect the cause of the interruption.
Check the machine sequence and related main-circuit components, including the magnetic contactor. FANUC documentation notes that this overvoltage condition can occur if the main-circuit power supply is switched off while the emergency-stop state is released.
5. Determine Whether the Amplifier Requires Repair or Replacement
The point at which the alarm occurs helps narrow the diagnosis:
- Alarm during acceleration or deceleration: Check input voltage stability, PSM capacity, power-source impedance, and spindle parameters first.
- Alarm before the spindle starts: A spindle amplifier fault may be present. The spindle amplifier should be professionally tested and repaired or replaced as required.
- Spindle amplifier alarm 11 and PSM alarm 7 occur together: Diagnose the common power supply module according to FANUC alarm 7 procedures. Power supply module repair or replacement may be required.
- No improvement after voltage, capacity, sequence, and parameter checks: Test the spindle amplifier and replace it if confirmed faulty.
Do not replace the spindle amplifier before checking the common power supply and machine configuration. SP9011 can be generated by an external power-supply or selection problem rather than by the spindle amplifier alone.
FANUC SP9011 Troubleshooting Summary
Use the following order when diagnosing FANUC SP9011:
- Confirm spindle amplifier alarm 11 and check whether the PSM displays alarm 7.
- Measure the input voltage and observe voltage variation during spindle deceleration.
- Confirm that the common power supply module has sufficient capacity.
- Check spindle initialization, test P4672 as instructed, and verify the motor-specific parameters.
- Inspect the main-circuit shutdown sequence and magnetic contactor if an abnormal power interruption occurred.
- Professionally test the spindle amplifier or power supply module and repair or replace the confirmed faulty unit.
Technical References
- FANUC AC Servo Motor αis/αi Series, AC Spindle Motor αi Series, Servo Amplifier αi Series Maintenance Manual, B-65285 series
- FANUC AC Spindle Motor αi/βi Series Parameter Manual, B-65280CM
Always use the manual edition that applies to the exact CNC, spindle motor, spindle amplifier, and power supply module installed on the machine.
For related spindle alarm numbers, see the FANUC Serial Spindle Alarm Codes SP9001–SP9033.
Need Help With FANUC Spindle Amplifier Repair?
REACO CNC provides testing and repair support for FANUC spindle amplifiers and power supply modules. Send us the CNC alarm number, amplifier LED display, exact amplifier model, motor model, and a description of when the alarm occurs so our technicians can evaluate the fault.
