Mitsubishi Electric MELSERVO-J4 (MR-J4) alarm AL.50: Overload 1
Alarm AL.50 on a Mitsubishi MR-J4 servo amplifier is Overload 1: the load exceeded the overload protection characteristic of the servo amplifier. Details 50.1–50.3 occur during operation, 50.4–50.6 during a stop.
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When it happens
- During operation (50.1–50.3): sustained high effective load
- During a stop (50.4–50.6): holding against a collision, gravity or hunting in servo-lock
Reading the subset
| Subset | What it tells you |
|---|---|
| 50.1 / 50.2 / 50.3 | Thermal overload error 1 / 2 / 4 during operation. |
| 50.4 / 50.5 / 50.6 | Thermal overload error 1 / 2 / 4 during a stop. |
Likely causes and checks
1Motor power cable disconnected or U/V/W wired wrongly
- Points to it
- Alarm soon after wiring work; motor turns poorly.
- Check
- Check the servo motor power cable and the U/V/W wiring.
2Electromagnetic brake not released
- Points to it
- Motor runs hot from the first move; brake click not heard.
- Check
- Check that the electromagnetic brake is released during operation.
3Continuous current above the amplifier rating
- Points to it
- High effective load ratio; alarm late in the cycle.
- Check
- Check the effective load ratio in MR Configurator2; reduce the load or use a larger capacity motor.
4Servo system unstable and resonating, or hunting in servo-lock
- Points to it
- Noise or vibration from the axis; for 50.4, hunting at standstill.
- Check
- Check for resonance or hunting and adjust the gains.
5Collision with the machine (during a stop)
- Points to it
- Detail 50.4 with the axis against an obstruction.
- Check
- Check whether a moving part collided with the machine.
6Wrong encoder cable destination (multi-axis) or linear encoder polarity
- Points to it
- Commissioning or MR-J4W unit.
- Check
- Check the CN2A/CN2B/CN2C connections and the linear encoder mounting polarity.
Telling it apart
- AL.50 is accumulated overload against the protection characteristic; AL.51 (Overload 2) is maximum output current flowing continuously, typically from a collision or torque saturation.
- Warning AL.E1 (Overload warning 1) is shown before the overload alarm; it means the load is approaching the limit.
- Let the equipment cool for about 30 minutes after removing the cause; resetting repeatedly can damage the amplifier and motor.
Evidence to collect
- Full alarm and detail number (running or stopped)
- Effective and peak load ratio from MR Configurator2
- Brake release confirmation
- Whether the axis was hunting or touching a stop
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