SP0003

Power OFF the machine completely. Disconnect the spindle motor power cables (U, V, W) from the spindle amplifier output terminals. Use a megohm insulation tester set to 500VDC and test each motor winding (U-V, V-W, W-U) and each phase to ground. Resistance should be >10MΩ. Values <1MΩ indicate insulation failure.

Discharge amplifier capacitors by waiting 5 minutes after power-off before disconnecting cables. High voltage present.

Measure spindle motor winding resistance with a multimeter. Disconnect motor from amplifier. Measure U-V, V-W, W-U. Resistance should be balanced (typically 0.1-5Ω depending on motor size). Variance >10% between phases or reading <0.1Ω indicates shorted windings.

Inspect spindle motor power cable for physical damage, coolant contamination, or worn insulation. Check cable routing for pinch points at cable carriers and through machine structure. Replace cable if any insulation damage is visible.

If motor and cable test good, locate the blown fuse on the spindle amplifier (typically marked F1, F2, or FU on alpha or beta series amplifiers). Replace with exact Fanuc-specified fast-acting fuse rating. Check amplifier LED status: steady red indicates amplifier fault. Reset alarm via SYSTEM > ALARM > HISTORY, power cycle, and monitor for recurrence.

Never use higher amperage fuses or bypass fuse protection. This will damage amplifier power modules.

With spindle motor disconnected from amplifier, replace the blown fuse. Power ON the machine and observe amplifier LED codes. If alarm SP0003 recurs immediately without motor connected, the amplifier power stage is faulty.

Ensure motor is fully disconnected before this test to isolate amplifier from motor faults.

Check DIAGNOSIS > SPINDLE screen for spindle load current values (monitor while attempting spindle rotation at low speed if motor tests good). Excessive current >150% of motor rated current with no load indicates amplifier transistor leakage or control circuit malfunction.

Inspect amplifier cooling fan operation and heat sink cleanliness. Blocked airflow or failed fans cause power module overheating and premature failure. Clean heat sinks with compressed air and verify fan rotation. Check fan voltage at connector (typically 24VDC).

If amplifier is confirmed faulty, check spindle parameters before replacement: parameter 4001 (spindle motor code), 4002 (rated speed), 4004 (rated current). Record DIAGNOSIS > PARAMETER > SP PARAM values. Replace amplifier with identical Fanuc model and restore parameters from backup or manual entry.

Amplifier replacement requires parameter restoration and spindle orientation setup. Record parameters before removal.

Manually rotate the spindle by hand (belt or direct coupling) with power OFF and amplifier disconnected. Rotation should be smooth with slight resistance from encoder drag. Hard spots, grinding noise, or inability to rotate indicate bearing seizure or mechanical obstruction.

Remove all tools and open collet/chuck before manual rotation attempt.

Check DIAGNOSIS > SPINDLE > LOAD METER data from alarm history if available. Spindle load >100% immediately before alarm indicates mechanical overload. Check SYSTEM > ALARM > HISTORY for preceding alarms (SV0440 spindle overload, PS0011 position encoder fault).

Inspect spindle belt tension if belt-driven. Over-tensioned belts cause excessive bearing preload and motor current. Check belt tension per machine manufacturer specifications (typically 10-15mm deflection with 5kg force). Replace worn or glazed belts.