9 Troubleshooting
9-30
Abnormal Noise
from Servomotor
The servomotor largely vibrated
during execution of tuning-less
function.
Check the motor speed waveform.
Reduce the load so that the moment
of inertia ratio becomes within the
allowable value, or increase the
load level or lower the tuning level
for the tuning-less levels setting
(Fn200).
Mounting is not secured.
Check if there are any loose mount-
ing screws.
Tighten the mounting screws.
Check if there is misalignment of
couplings.
Align the couplings.
Check if there are unbalanced cou-
plings.
Balance the couplings.
Bearings are defective.
Check for noise and vibration
around the bearings.
Replace the servomotor.
Vibration source at the driven
machine.
Check for any foreign matter, dam-
age, or deformations on the machin-
ery's movable parts.
Contact the machine manufacturer.
Noise interference due to incorrect
I/O signal cable specifications.
The I/O signal cable must be tinned
annealed copper shielded twisted-
pair or screened unshielded twisted-
pair cable with a core of 0.12 mm
2
min.
Use the specified I/O signal cable.
Noise interference due to length of
I/O signal cable.
Check the length of the I/O signal
cable.
Make the I/O signal cable length
less than 3 m.
Noise interference due to incorrect
cable specifications of encoder
cable.
The encoder cable must be tinned
annealed copper shielded twisted-
pair or screened unshielded twisted-
pair cable with a core of 0.12 mm
2
min.
Use the specified encoder cable.
Noise interference due to length of
encoder cable.
Check the length of the encoder
cable.
The encoder cable must be no more
than 50 m.
Noise interference due to damaged
encoder cable.
Check if the encoder cable is bent
and the sheath is damaged.
Replace the encoder cable and cor-
rect the cable layout.
Excessive noise to the encoder
cable.
Check if the encoder cable is bun-
dled with a high-current line or near
a high-current line.
Correct the cable layout so that no
surge is applied.
The FG potential varies because of
influence from machines on the ser-
vomotor side, such as the welder.
Check if the machines are correctly
grounded.
Properly ground the machines to
separate from the encoder FG.
SERVOPACK pulse counting error
due to noise interference
Check if there is noise interference
on the I/O signal line from the
encoder.
Take measures against noise in the
encoder wiring.
Excessive vibration and shock to
the encoder
Check if vibration from the machine
occurred or servomotor installation
is incorrect (mounting surface accu-
racy, fixing, alignment, etc.).
Reduce vibration from the machine,
or secure the servomotor installa-
tion.
An encoder fault occurred. − Replace the servomotor.
(cont’d)
Problem Probable Cause Investigative Actions Corrective Actions
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