Skills and methods for judging Mitsubishi servo motor encoder failure

Common troubleshooting methods

AL.10 Undervoltage

The power supply voltage is too low. MR-E-□A: Below 160V



·The power supply voltage is too low. →Check the power system

·The instantaneous power failure of the control power supply is more than 60ms. →Check the power system

·Due to too small power supply capacity, the power supply voltage drops during startup. →Check the power system

·The power is turned off and then back on within 5 seconds. →Check the power system

• There is an internal failure in the servo amplifier. →Replace the servo amplifier

AL.12 Memory error 1. →Replace servo amplifier

AL.13 The clock is abnormal, → replace the servo amplifier

AL.14 Watchdog abnormal, → replace the servo amplifier

AL.15 Memory error 2 → Replace the servo amplifier

Skills and methods for judging Mitsubishi servo motor encoder failure

AL.12: RAM ROM abnormal

AL.13: Abnormal printed circuit board

AL.14: CPU exception

AL.15: EEPROM abnormal

·The servo amplifier is faulty. Replace the servo amplifier.

AL.16 Encoder abnormal 1

The communication between the encoder and servo amplifier is abnormal.

The main reason

·The connector CN2 is not connected properly. → Wire correctly.

· Encoder failure. →Replace the servo motor.

· The encoder cable is faulty. (Open circuit or short circuit) → Repair or replace the cable.

• The coordination between the servo amplifier and the servo motor is incorrect. →Use the correct fit

AL.17 circuit board abnormal 2,

AL.19 Memory Abnormal 3

AL.17: CPU and parts abnormal

AL.19: ROM memory is abnormal

The main reason

• Internal failure of the servo amplifier. →Replace the servo amplifier.

AL.1A Motor coordination is abnormal

The coordination between the servo amplifier and the servo motor is incorrect.

Skills and methods for judging Mitsubishi servo motor encoder failure

The main reason

• The coordination between the servo amplifier and the servo motor is incorrect. → Use the correct fit.

·The servo motor selected by parameter No.0 does not match the currently used servo amplifier. →Set parameter No.0 correctly.

AL.20 Encoder abnormal 2

The communication between the encoder and servo amplifier is abnormal.



·Encoder connector CN2 is not connected properly. → Wire correctly.

Encoder cable failure (open circuit or short circuit) → repair or replace the cable

· Encoder failure. →Replace the servo motor.

AL.24 The main circuit is abnormal

The servo motor output terminal (U·V·W phase) has a ground fault.



• There is a break in the power input and output wiring on the main circuit terminal (TE1). →Repair the wires.

· The surface of the servo motor power line is damaged. →Replace the wire.

• The main circuit of the servo amplifier is malfunctioning. →Replace the servo amplifier.

The braking current exceeds the allowable value of the built-in regenerative braking resistor or regenerative braking option.

The regenerative brake transistor is abnormal.

Content: The braking current exceeds the allowable value of the built-in regenerative braking resistor or regenerative braking option.



·The parameter No.0 setting is wrong. →Set parameter No.0 correctly.

·The built-in regenerative braking resistor or regenerative braking option is not connected. → Wire correctly.

·The power supply voltage is abnormal (260V or more). →Check the power supply.

Skills and methods for judging Mitsubishi servo motor encoder failure

·High-frequency or continuous regenerative braking operation causes the regenerative current to exceed the allowable value of the built-in regenerative braking resistor or regenerative braking option. →Reduce braking frequency. →Replace the regenerative braking resistor or regenerative braking option with large capacity. →Reduce the load.

Content: The regenerative brake transistor is abnormal.



·Built-in regenerative braking resistor or regenerative braking option failure. →Replace the servo amplifier or regenerative brake option.

·The regenerative braking transistor is malfunctioning. →Replace the servo amplifier.

AL.25 Absolute position data is lost The battery cable is loose or the voltage is low

AL.30 Regenerative alarm Check the regenerative energy consumption circuit and reduce the load

AL.31 Overspeed

The speed exceeds the instantaneous allowable speed.



·The command input pulse frequency is too high. →Set the command pulse frequency correctly.

·The acceleration/deceleration time is too small and the overshoot is too large. →Increase the acceleration/deceleration time constant.

·The servo system is unstable and causes overshoot. →Reset the gain. When the gain cannot be reset: ①The load moment of inertia is smaller than the set value. ②Recheck the setting of acceleration and deceleration time constant.

·The electronic gear ratio is too large. (Parameter No. 3, No. 4) → Set correctly.

· Encoder failure. →Replace the servo motor.

Parameter No.3

For the parameters marked with *, the power must be turned off after setting, and then turned on again to make the parameters take effect.

Electronic gear (command pulse magnification numerator)

Incorrect setting of the electronic gear may result in erroneous operation. The setting must be made with the servo amplifier stopped.

Set the corresponding magnification for the input command pulse.

Skills and methods for judging Mitsubishi servo motor encoder failure

(Note) The setting range is: 1/50

The setting of the number of input pulses per revolution of the servo motor in the following formula can be changed.

(Example) HC-KFE series: 10000 pulse/rev

If the set value is 0, this parameter can be automatically set according to the resolution of the connected servo motor.

Initial value: 1

Setting range: 0, 1~65535

AL.32 Overcurrent

The output current of the servo amplifier exceeds the allowable current.



• There is a short circuit in the U, V, and W phases on the output side of the servo amplifier. → Wire correctly.

• The U, V, and W phases on the output side of the servo amplifier are grounded. → Wire correctly.

• Due to the interference of external noise, the overcurrent detection circuit has an error. →Implement anti-interference treatment.

• The servo amplifier transistor (IPM) is malfunctioning. →Replace the servo amplifier.

AL.33 Overvoltage

The input of the DC bus voltage is above 400V.



· The wiring of the built-in regenerative braking resistor or regenerative braking option is open or poorly connected. →Replace the wire. → Wire correctly.

·Regeneration brake transistor failure →Replace the servo amplifier.

·The wiring of the built-in regenerative braking resistor or regenerative braking option is broken. →When using the built-in regenerative braking resistor, replace the servo amplifier. →When using the regenerative brake option, replace the regenerative brake option.

·The capacity of the built-in regenerative braking resistor or regenerative braking option is insufficient. →Use the regenerative brake option or replace it with a larger capacity regenerative brake option.

• The power supply voltage is too high. →Check the power system

AL.35 Command pulse frequency is abnormal

The pulse frequency of the input command pulse is too high.



·The command pulse frequency is too high. → Change the command pulse frequency to a proper value.

• The command pulse is mixed with noise. →Implement anti-interference treatment.

· The command device is malfunctioning. →Replace the command device.

AL.37 Parameter abnormal

The parameter setting value is abnormal.

Skills and methods for judging Mitsubishi servo motor encoder failure



·The parameter setting value has changed due to a malfunction of the servo amplifier. →Replace the servo amplifier.

·The regenerative brake option selected by parameter No.0 is not connected. →Set parameter No.0 correctly.

Parameter No.0

For the parameters marked with *, the power must be turned off after setting, and then turned on again to make the parameters take effect.

*Control mode·Regenerative braking option selection:

Select the motor capacity, motor series, control mode, and regenerative braking option.

□ □ □ □

*1 *2 *3 *4

*1 Select motor capacity

0:100W

1:200W

2: 400W

3:500W

4:750W

5:1KW

6: 1.5KW

7: 2KW

*2 Select the regenerative brake option

0: no

1: Standby (please do not set)

2: MR-RB032

3:MR-RB12

4: MR-RB32

5: MR-RB30

6: MR-RB50

*3Select motor series

0: KFE

1: SFE

*4 Select control mode

0: location

1: position and speed

2: speed

Initial value: 0000(MR-E-10A), 1000(MR-E-20A), 2000(MR-E-40A), 4000(MR-E-70A), 5010(MR-E-100A), 6010( MR-E-200A),

Setting range: 0000h~7912h

The main circuit components are abnormally overheated.



• The servo amplifier is abnormal. →Replace the servo amplifier.

Skills and methods for judging Mitsubishi servo motor encoder failure

· Repeatedly pass "ON-OFF" under overload status to continue operation. →Check the operation method.

• The cooling fan of the servo amplifier stops operating. →Repair the cooling fan of the servo amplifier.

AL.42 Feedback alarm The encoder signal is lost → replace the servo motor

AL.45 The main circuit is overheated. Check the cooling system, drive method, and replace the servo amplifier.

AL.46 Servo motor is overheated

Servo motor temperature rise thermal protection action.



·The ambient temperature of the servo motor exceeds 40 degrees. → Make the working environment temperature of the servo motor work between 0-40 degrees.

· The servo motor is overloaded. →Reduce the load. →Check the operating mode. → Replace the servo motor with a larger power.

· The thermal protection device in the encoder is faulty. The cooling fan of the servo motor is abnormal → replace the servo motor.

AL.50 Overload 1

Exceeds the carrying capacity of the servo amplifier.

Load rate 300%: 2.5s or more

200% load rate: more than 100s



·Servo amplifier is used in occasions where the load is greater than its continuous output capacity. →Reduce the load. →Check the operating mode. → Replace the servo motor with a larger power.

·The servo system is unstable and vibrates. → Perform several accelerations and decelerations to complete the automatic gain adjustment. →Modify the response speed of automatic gain adjustment. →Stop automatic gain adjustment. The gain adjustment should be done manually.

· Mechanical failure. →Check the operating mode. →Install the limit switch.

·The wiring of the servo motor is incorrect. The output U·V·W of the servo amplifier and the input U·V·W of the servo motor are not connected in phase. → Wire correctly.

· Encoder failure. →Replace the servo motor.

Encoder failure: stop the output of the servo motor, slowly rotate the shaft of the servo motor, and the accumulated value of the feedback pulse at this time

Should be proportional to the angle of rotation, it can be judged that the encoder is faulty.

Skills and methods for judging Mitsubishi servo motor encoder failure

AL.51 Overload 2 Check the operating parameters, connect correctly, adjust the acceleration and deceleration time, replace the servo amplifier, and replace the servo motor

AL.52 error is too large

The stuck pulse in the deviation counter exceeds the resolution capability of the encoder × 10 (pulse).



·The acceleration/deceleration time constant is too small. →Increase the acceleration/deceleration time constant.

·The torque limit value (parameter No.28) is too small. →Increase the torque limit value.

·Due to the drop of the power supply voltage, the torque is insufficient and the servo motor cannot be started. →Check the capacity of the power supply. → Replace the servo motor with a larger power.

·The value of position control gain 1 (parameter No.6) is too small. →Adjust the set value to the range where the servo system can operate correctly.

·The shaft of the servo motor rotates due to external force. →When the torque limit is reached, increase the torque limit value. →Reduce the load. →Choose a more powerful servo motor.

· Mechanical conflict. →Check the operating mode. →Install the limit switch.

· Encoder failure. →Replace the servo motor.

·The wiring of the servo motor is incorrect. The output U·V·W of the servo amplifier and the input U·V·W of the servo motor are not connected in phase. → Wire correctly.

Parameter No.28

For the parameters marked with *, the power must be turned off after setting, and then turned on again to make the parameters take effect.

Internal torque limit 1:

Set maximum torque=100%.

Used to limit the maximum output torque of the servo motor.

If set to 0, no torque is output.

Initial value: 100%

Setting range: 0~100%

Used to set the gain of position loop 1.

If the gain becomes larger, the tracking ability of the position command is also enhanced.

During automatic adjustment, this parameter will be automatically set as the result of automatic adjustment.

Initial value: 35 rad/s

Setting range: 4~2000 rad/s

AL.73 Auxiliary pulse frequency alarm The pulse input must reach 600KPPS

AL.74 The option card memory is abnormal → replace the option card board

AL.75 Option card memory abnormal 2→Replace option card board

AL.8A serial communication timeout

The time of RS-232C or RS-422 communication interruption exceeds the setting value of parameter No.56.



· The communication cable is broken. →Repair or replace the communication cable.

·The communication cycle is longer than the setting value of parameter No.56. →Set the parameters correctly.

· Communication protocol error. →Modify the communication protocol.

Parameter No.56

For the parameters marked with *, the power must be turned off after setting, and then turned on again to make the parameters take effect.

Serial communication timeout selection:

It is used to set the time of communication timeout [S].

If it is set to 0, then no timeout check is performed.

Initial value: 0

Setting range: 0, 1~60 s

AL.8E Serial communication is abnormal

A communication error occurred between the servo amplifier and communication equipment (computer, etc.).



· The communication cable is faulty. (Open circuit or short circuit) → Repair or replace the cable.

· Communication equipment (computer, etc.) is malfunctioning. →Replace communication equipment (computer, etc.).

88888 watchdog

The CPU/component is abnormal.



• Internal failure of the servo amplifier. →Replace the servo amplifier.

AL.90 Zero setting error Zero reset, reconfirm the zero position

AL.96 Zero setting error reduces the influence of interference

AL.9A digital switch alarm, set parameters correctly

AL.9F battery alarm: battery voltage is too low, replace with new product, good battery 3.6V