Mitsubishi Electric MELSERVO-J4 (MR-J4) alarm AL.51: Overload 2
Alarm AL.51 on a Mitsubishi MR-J4 servo amplifier is Overload 2: maximum output current flowed continuously due to a machine collision or similar. Detail 51.1 occurs during operation and 51.2 during a stop.
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When it happens
- During operation when the axis hits an obstruction or the torque saturates
- During a stop when the axis is pushing against a hard stop
Reading the subset
| Subset | What it tells you |
|---|---|
| 51.1 | Thermal overload error 3 during operation. |
| 51.2 | Thermal overload error 3 during a stop. |
Likely causes and checks
1Collision with the machine
- Points to it
- Alarm at a fixed position; marks on the mechanism.
- Check
- Check whether a moving part collided and review the operation pattern.
2Motor power cable disconnected or U/V/W wired wrongly
- Points to it
- After maintenance; motor cannot make torque.
- Check
- Check the servo motor power cable and U/V/W wiring.
3Encoder cable connected wrongly
- Points to it
- Multi-axis unit or after a cable change.
- Check
- Check the encoder cable connection.
4Torque insufficient (saturated)
- Points to it
- Peak load ratio at the limit during the move.
- Check
- Check the peak load ratio; reduce the load, review the operation pattern or use a larger motor.
5Amplifier or motor/encoder failure
- Points to it
- Load and wiring check good.
- Check
- Replace the amplifier and check repeatability, then the servo motor.
Telling it apart
- AL.51 is maximum current held continuously (collision, saturation); AL.50 is accumulated load over the protection curve.
- If AL.52 (Error excessive) appears in the same event, the axis was blocked and could not follow the command.
Evidence to collect
- Full alarm and detail number
- Peak load ratio and position at the alarm
- Inspection of the mechanism for collision
- Wiring check results
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