03 ALARM — DC LINK FUSE BLOWN / MAIN CIRCUIT OVERLOAD

Identify which module displays the '03' alarm. If it is on the Power Supply (PSM/Converter) indicating a main circuit overload, check the load meter. If the motor is operated beyond its continuous rating or subject to excessive acceleration/deceleration, modify the CNC program to reduce the cutting load or increase the acceleration/deceleration time constant.

If the '03' alarm is on the Spindle Amplifier and occurs immediately when canceling the emergency stop (or when the magnetic contactor turns on then immediately off), inspect the DC link wiring. Verify that the DC link terminal cables are connected correctly and securely without errors.

If the DC link wiring is secure but the alarm still occurs when canceling the emergency stop, inspect the communication interface cable (e.g., JX1B-JX1A) between the Power Supply and Spindle Amplifier. If the cable is damaged or pin 9 is short-circuited to 0V, replace the interface cable.

If the '03' alarm occurs during spindle operation (rotation), disconnect the motor power leads (U, V, W) from the amplifier. Measure the insulation resistance between each power lead and ground (PE) using a megohmmeter. If a short circuit or ground fault is detected, replace the power cable.

If the power cable is normal, disconnect the power cable from the motor terminals and measure the insulation resistance between the motor windings (U, V, W) and the motor ground. If the motor winding is short-circuited to ground, replace the spindle motor.

If the external wiring, cables, and motor are completely normal, the DC link fuse inside the Spindle Amplifier has blown due to a destroyed internal power element (IGBT or IPM module failure). Replace the Spindle Amplifier module.

If none of the above steps resolved the alarm, contact an authorized FANUC service representative.