Mitsubishi Electric MELSERVO-J3 Series Instruction Manual page 364

11. TROUBLESHOOTING
Display Name
A20 Encoder error 2
(during runtime)
A21 Encoder error 3
(during runtime)
Definition
Communication 1. Encoder cable disconnected.
error occurred <Check method>
between encoder Check the encoder cable connection.
and servo amplifier.
2. Encoder cable 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 and
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.
Error occurred in 1. An excessive acceleration occurred
encoder. due to oscillation, etc. is detected by
the encoder
<Check method>
Check if servo motor vibration and
unusual noise, etc. is occurring.
2. An error in the detection circuit of the
encoder.
Cause
11 - 7
Action
Connect servo amplifier
connector (CN2) and servo
motor encoder connector
correctly.
Repair or change the cable.
1. Reduce the position loop
gain.
2. Decrease the auto tuning
response level.
Change the servo motor.
Take the grounding and
noise reduction techniques.
1. Reduce the position loop
gain.
2. Decrease the auto tuning
response level.
Change the servo motor.
(Note 2)
Alarm
detailed
information
47
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