Mitsubishi Electric MELSERVO-J3 Series Instruction Manual page 663

16. INDEXER POSITIONING OPERATION
Display Name
Communication
A20 Encoder error
error occurred
2 (during
between
runtime)
encoder and
servo amplifier.
Encoder error An error
A21
3 (during occurred in
runtime)) encoder.
Definition
1. The encoder cable was disconnected.
<Check method>
Check the encoder cable connection.
2. Encoder cable is faulty.
<Check method>
Check if the encoder cable is disconnected or
shorted.
3. An excessive acceleration occurred due to
oscillation, etc. is detected by the encoder.
<Check method>
Check if servo motor vibration or unusual noise, etc.
is occurring.
4. Encoder fault.
5. External noise caused a communication error.
<Check method>
1. Check that the encoder cable and the power
cable run in parallel.
2. Check if the environment is affected by the noise
of surrounding electromagnetic valve, magnetic
contactor, relay, etc.
3. Check the servo amplifier and servo motor for
grounding.
4. Check if there is a factor causing surrounding
static electricity.
5. Check shield procedure of the encoder cable.
1. An excessive acceleration occurred due to
oscillation, etc. is detected by the encoder.
<Check method>
Check if servo motor vibration or unusual noise, etc.
is occurring.
2. A fault in the detection circuit of the encoder.
Cause
16 - 108
(Note 2)
Alarm
Action
detailed
information
Connect the servo
amplifier connector
(CN2) and the servo
motor encoder
connector correctly.
Repair or replace the
cable.
1. Reduce the position
loop gain.
2. Decrease the auto
tuning response
setting.
Change the servo
motor.
Take the grounding and
noise reduction
techniques.
1. Reduce the position
loop gain.
2. Decrease the auto
tuning response
setting.
Change the servo
motor.
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