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MELSEC-Q
15 TROUBLESHOOTING
Classifica
tion of
errors
Error
code
LED
indicator
of servo
amplifier
Error name Description Cause
The encoder connecter (CN2) is
disconnected.
Fault in the encoder.
2020 20 Encoder error 2
Communication error occurred
between encoder and servo amplifier.
Encoder cable fault. (Wire breakage
or shot)
Power input wires and servomotor
power wires are in contact.
Sheathes of servomotor power
cables deteriorated, resulting in
ground fault.
2024 24 Main circuit error
Ground fault occurred at the
servomotor power (U, V and W
phases) of the servo amplififer.
Main circuit of servo amplifier failed.
Voltage low in the super capacitor in
the encoder.
Battery voltage low.
Absolute position data in error.
Battery cable or battery fault.
2025 25
Absolute position
lost
Power was switched on for the first
time in the absolute position detection
system.
Home position not set.
Parameter "
Pr.102
Regenerative
brake resistor" setting value error.
Built-in regenerative brake resistor
or regenerative brake option is not
connected.
High-duty operation or continuous
regenerative operation caused the
permissible regenerative power of
the regenerative brake option to be
exceeded.
Power supply voltage is abnormal.
MR-J3-B : 260VAC or more
MR-J3-B1: 135VAC or more
Permissible regenerative power of the
built-in regenerative brake resistor or
regenerative brake option is
exceeded.
Built-in regenerative brake resistor
or regenerative brake option faulty.
Servo
amplifier
errors
2030 30
Regenerative
error
Regenerative transistor fault Regenerative transistor faulty.