8-8
8-3 Troubleshooting
8
Troubleshooting
18 Regeneration 
overload
Occurs when the Ser-
vomotor is decelerat-
ing.
• Load inertia is too large. • Calculate the regenera-
tive energy, and connect 
an External Regenera-
tion Resistor with the re-
quired regeneration 
absorption capacity.
• Extend the deceleration 
time.
• The deceleration time is 
too short.
• The Servomotor rotation 
speed is too high.
• Reduce the Servomotor 
rotation speed.
• Extend the deceleration 
time.
• Calculate the regenera-
tive energy, and connect 
an External Regenera-
tion Resistor with the re-
quired regeneration 
absorption capacity.
• The operating limit of the 
External Regeneration 
Resistor is limited to 
10%.
• Set Pn6C to 2.
For details, refer to Param-
eter Details on page 5-32.
Occurs during descent 
(vertical axis).
• Gravitational torque is 
too large.
• Add a counterbalance to 
the machine to lower 
gravitational torque.
• Slow the descent speed.
• Calculate the regenera-
tive energy, and connect 
an External Regenera-
tion Resistor with the re-
quired regeneration 
absorption capacity.
• The operating limit of the 
External Regeneration 
Resistor is limited to 
10%.
• Set Pn6C to 2.
For details, refer to Param-
eter Details on page 5-32.
21 Encoder 
disconnection 
detected
Occurs during opera-
tion.
• The encoder is discon-
nected.
• Connector contacts are 
faulty.
• Fix the locations that are 
disconnected.
• Correct the wiring.
• The encoder wiring is in-
correct.
• Correct the wiring.
• The encoder is dam-
aged.
• Replace the Servomotor.
• The Servo Drive is faulty. • 
Replace the Servo Drive.
• The Servomotor is 
me-
chanically being held.
• If the Servomotor shaft is 
being held by external 
force, release it.
Alarm
code
Error
Status when error 
occurs
Cause Countermeasure