3A ALARM — Overcurrent

Check the machine for vibration during operation. If vibration is occurring, lower the speed loop gain parameter (SV005 / VGN1) to an appropriate value or apply a machine resonance suppression filter.

Verify the current loop gain parameters (SV009, SV010, SV011, SV012) against the standard values for the motor and correct them if necessary. If the current feedback exceeds the command during acceleration or deceleration, lower the inductive voltage compensation gain (SV047 / EC).

Inspect the motor power line (U, V, W terminals) and the detector cables. Ensure the U, V, W phase order is correct and that the cables are not mistakenly crossed with another axis motor. Securely reconnect any incorrect wiring.

Disconnect the U, V, W power lines from the drive unit terminal block and the motor's cannon plug. Use a multimeter to test for short circuits between phases and ground faults to the frame ground (FG). If the cable is faulty, replace the motor power cable.

Reconnect the cannon plug to the motor. Test the insulation resistance between the power cable and the ground (FG) using a megger tester. If a ground fault is detected within the motor, replace the motor (and establish the zero point if using an absolute position system).

If applied to a spindle drive, check the load meter on the CNC screen to ensure the cutting load does not exceed the motor's maximum output. Verify that the unit capacity matches the motor using parameter SP039, and reduce the cutting load if it is excessive.

If the alarm persists, the drive unit's internal power module or the detector is likely defective due to environmental factors (e.g., cutting fluid, incomplete grounding). Improve the installation environment, replace the MDS-C drive unit or detector, and contact authorized Mitsubishi service.