Mitsubishi MR-J4 AL.52: Error excessive after wiring work, what to check?
I'm getting an AL.52 'Error excessive' alarm on my Mitsubishi MR-J4 servo amplifier. This started happening right after I rewired the servo motor. The axis doesn't move at all before the alarm trips.
The AL.52 alarm on a Mitsubishi MR-J4 servo amplifier indicates an excessive following error, meaning the difference between the commanded and actual position has exceeded the alarm level. This often occurs during acceleration if the time constant is too short, when a torque limit is active, or if the axis is blocked. Given that the alarm appeared after wiring work and the axis doesn't move, the most likely cause is a wiring issue.
Likely causes and checks
1Motor power or encoder cable disconnected or wired wrongly
- Points to it
- This is the most common cause when the alarm appears immediately after wiring work and the axis shows no movement.
- Check
- Check the servo motor power cable, U/V/W wiring, and the encoder cable connection for proper installation and continuity.
2Torque limit active, or brake not released
- Points to it
- If the torque limit is active or the brake is engaged, the motor will not be able to move the load, leading to an excessive position error.
- Check
- Check whether the torque limit is in effect and whether the electromagnetic brake is released.
3Collision or insufficient torque
- Points to it
- A physical obstruction or an inability of the motor to provide enough torque for the load can cause the actual position to lag significantly behind the commanded position.
- Check
- Check for any collisions or obstructions in the axis's path and review the peak load ratio. Consider reducing the load or adjusting the operation pattern.
4Acceleration/deceleration time constant too short, or position loop gain too small
- Points to it
- If the system is commanded to accelerate too quickly or the position loop gain is set too low, the servo system may not be able to follow the command accurately, leading to a large following error.
- Check
- Lengthen the acceleration/deceleration time constant and check repeatability. Alternatively, increase the position loop gain [Pr. PB08].
Next check: Given that the alarm occurred immediately after wiring work and the axis does not move, start by thoroughly inspecting all connections for the servo motor power cable (U/V/W) and the encoder cable. Ensure they are correctly wired and securely connected.
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