Mitsubishi Servo driver Controller Alarm Codes and Troubleshooting Methods

Below are 3 common Mitsubishi servo drive alarm codes and how to resolve them:

1. Alarm Code AL31.1 (A.31.1)

Phát: Motor overspeed alarm.
Possible Causes & Solutions:

• Cause 1: Input pulse frequency is too high.
  Giải pháp: Set the correct pulse frequency.

• Cause 2: Acceleration/deceleration time is too short, causing overshoot.
  Giải pháp: Increase acceleration/deceleration time constants.

• Cause 3: Servo system is unstable.
  Giải pháp: Reconfigure the gain settings.

• Cause 4: Electronic gear ratio is too large.
  Giải pháp: Set the correct electronic gear ratio.

Cause 5: Encoder malfunction.
Giải pháp: Replace the Mitsubishi servo encoder or motor.

2. Alarm Code ALE6 / 6.1 (A.E6 or A.E6.1)

Phát: Emergency stop triggered on the Mitsubishi servo motor.
Possible Causes & Solutions:

• Cause 1: EMG and SG terminals on CN1 are not connected.
  Giải pháp: Connect EMG to SG on CN1.

• Cause 2: 24V power supply for the control circuit is not connected.
  Giải pháp: Supply the required 24V power.

3. Alarm Code AL52 (A.52)

Phát: Excess pulses stored in the deviation counter exceed encoder capacity ×10.
Possible Causes & Solutions:

• Cause 1: Improper acceleration/deceleration time constant.
  Giải pháp: Set appropriate values (refer to user manual).

• Cause 2: Torque limit is too low.
  Giải pháp: Increase torque limit.

• Cause 3: Insufficient torque due to voltage drop, motor fails to start.
  Giải pháp: Use a higher-power servo motor.

• Cause 4: Position loop gain 1 is too low.
  Giải pháp: Adjust to an appropriate range for stable operation.

• Cause 5: External force caused motor shaft to rotate.
  Giải pháp: Increase torque limit, reduce load, or use a larger motor.

• Cause 6: Mechanical fault.
  Giải pháp: Check operating mode and install limit switches.

• Cause 7: Encoder failure.
  Giải pháp: Replace the encoder or the motor.

Mitsubishi AC Servo System Overview

• Main servo driver series: MR-ES, MR-J2S, MR-J3, MR-J2

Common Alarm Codes and Troubleshooting Summary:

1. AL.E6 / A.E6.1 – Emergency Stop

   • No 24V power or EMG-SG disconnected on CN1.

2. AL.37 (A.37) – Parameter Error

   • Internal parameter corruption; reset to factory settings.

3. AL.16 (A.16) – Encoder Fault

   • Encoder line or motor fault; reset parameters, check cables, replace encoder or driver.

4. AL.20 (A.20) – Encoder Error

   • Cable disconnect, loose connector, or CPU grounding failure in MR-J3; check cables, replace encoder.

5. AL.30 (A.30) – Regenerative Brake Fault

   • If alarm occurs at power-up, internal brake circuit is faulty; if during operation, check wiring or add an external brake resistor.

6. AL.50 (A.50), AL.51 (A.51) – Overload

   • Check U/V/W phase wiring, motor coils, grounding, load >100%, high response settings, or resonance.

7. AL.E9 (A.E9) – Main Circuit Disconnected

   • Check if main power is connected; if yes, main detection circuit may be faulty—replace drive or parts.

8. AL.52 (A.52) – Excessive Position Error

   • Common in oily/dusty environments; may be caused by encoder or drive output module failure.

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