My Mitsubishi MDS-E drive is continuously showing Alarm 50 and Alarm 51. What are the possible causes for these alarms, and what steps should I follow to troubleshoot the issue?

Receiving Alarm 50 (Overload 1) and Alarm 51 (Overload 2) on your Mitsubishi MDS-E drive can be due to several reasons. These alarms typically occur when the motor is overloaded or if there's an issue with the drive itself. You can follow these steps sequentially to troubleshoot the problem:

General Checks and Possible Causes:

• Overload Parameters: Check the parameters SV021 and SV022 for servo axes, and SP021 and SP022 for spindle axes. If these values are non-standard, adjust them according to your machine's specifications (Example Standard Values: Servo: 60/150, Spindle: 60/120, IPM: 300/100).
• Load Monitoring: Monitor the load values on the NC screen. If 'Max.current 3' on servo axes remains at maximum continuously, or if the load meter exceeds 120% for spindles, reduce the cutting amount, increase acceleration/deceleration time constants, or extend the cycle time.
• Mechanical Checks: Check if the machine is mechanically binding. Investigate and resolve issues like interference with positioning pins, a bent ball screw, or slide failure.
• Resonance and Hunting: Check for resonance or hunting in the machine. If resonance is present, adjust a notch filter and lower the speed loop gain (VGN1). If hunting occurs, increase VGN1 and decrease the speed loop lead compensation (VIA).
• Tool and Motor Capacity: Check tool life and replace if necessary. If the motor capacity is insufficient, adjust the cutting load or acceleration/deceleration rates.

Specific to Alarm 50 (Overload 1):

• Motor Brake: Check the motor brake relay and its associated connector (CN20). Correct wiring or replace the relay if the brakes are not releasing properly during operation.

Specific to Alarm 51 (Overload 2):

• Power Supply and Connections: With the main power off, verify that the PN voltage is correctly supplied to the drive. Ensure the L+/L- terminal screws are tight. Confirm that the motor power cables (U, V, W) and the encoder cable are connected correctly.
• Encoder Feedback: Check the encoder feedback. If droop on servo axes does not stabilize or the signal is abnormal, replace the encoder. For spindle axes, check the PLG output waveform.

Final Step:

• Hardware Failure: If all the above checks are normal and the alarms persist, there might be a hardware failure in the drive unit (MDS-E). In this case, you may need to replace the drive unit.