Mitsubishi Electric MELSERVO-J5 (MR-J5) alarm AL.052: Excessive error
Alarm AL.052 on a Mitsubishi MR-J5 servo amplifier is Excessive error: droop pulses exceeded the alarm occurrence level. It is the MR-J5 following-error alarm and corresponds to MR-J4 AL.52.
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When it happens
- During acceleration with a short time constant
- When the axis is blocked, a torque limit is active or the brake is applied
- At servo-on with the motor still moving, or at servo-off if an external force moves the axis (052.6)
Reading the subset
| Subset | What it tells you |
|---|---|
| 052.1 / 052.3 / 052.5 | Excessive droop pulse 1 / 2 / 3. |
| 052.4 | Excessive error during 0 torque limit. |
| 052.6 | Excessive droop pulse at servo-off. |
Likely causes and checks
1Motor power cable disconnected, U/V/W wiring loose or wrong, or encoder cable misconnected
- Points to it
- First move after maintenance.
- Check
- Check the U/V/W wiring for forgotten or loose screws and incorrect wiring, and the encoder cable connection.
2Torque limit active or electromagnetic brake not released
- Points to it
- Axis barely moves before the alarm.
- Check
- Check the torque limit value and that the brake releases during operation.
3Collision or insufficient torque
- Points to it
- Alarm at a fixed position or on the heaviest move.
- Check
- Check for interference and the peak load ratio; reduce the load or review the pattern.
4Acceleration time constant too short or position control gain too small
- Points to it
- Alarm only on fast moves.
- Check
- Lengthen the acceleration/deceleration time constant; increase [Pr. PB08].
5Excessive error alarm trigger level set wrongly
- Points to it
- Level changed from default.
- Check
- Check [Pr. PC01] and [Pr. PC06.3] ([G] [B]) or [Pr. PC24.3] and [Pr. PC43] ([A]).
6External force moving the shaft
- Points to it
- Vertical axis or belt-driven load; 052.6 at servo-off.
- Check
- Measure the actual position in servo-lock and review the machine.
Telling it apart
- Warning AL.09B (Excessive error warning) can precede AL.052.
- AL.052 with AL.051 in the same event points to a collision; AL.052 alone on fast moves points to time constant or gain.
Relevant parameters
| Parameter | Name | Why it matters |
|---|---|---|
| PB08 | Position control gain | Mitsubishi lists a gain that is too small as a cause. |
| PC01, PC06.3 ([G] [B]) / PC24.3, PC43 ([A]) | Excessive error alarm trigger level | Check it is set correctly. |
Evidence to collect
- Full alarm and detail number
- Droop pulse and torque trend
- Time constants and [Pr. PB08]
- Alarm level settings
- Brake and torque limit status
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