9 Troubleshooting
9-26
Servomotor
Moves
Instantaneously,
and then Stops
Servomotor wiring is incorrect.
Check the wiring.
Correct the wiring.
Encoder wiring is incorrect.
Check the wiring.
Correct the wiring.
Servomotor
Speed Unstable
Wiring connection to servomotor is
defective.
Check connections of power line
(phases U, V, and W) and encoder
connectors.
Tighten any loose terminals or con-
nectors and correct the wiring.
Servomotor
Rotates Without
Reference Input
Speed control: Speed reference
input is incorrect.
Check V-REF and SG to confirm if
the control method and the input are
agreed.
Correct the control method selec-
tion parameter, and the input signal.
Torque control: Torque reference
input is incorrect.
Check V-REF and SG to confirm if
the control method and the input are
agreed.
Correct the control method selec-
tion parameter, and the input signal.
Speed reference offset is incorrect.
The offset in the multi-winding
drive unit is adjusted incorrectly.
Adjust the offset in the multi-wind-
ing drive unit.
Position control: Reference pulse
input is incorrect.
Check the reference pulse form
(Pn200.0) and sign + pulse signal.
Correct the control method selec-
tion parameter, and the input signal.
A fault occurred in the multi-wind-
ing drive unit.
−
Replace the multi-winding drive
unit.
Dynamic Brake
Does Not Operate
Improper Pn001.0 setting
Check the setting for parameter
Pn001.0.
Correct the setting for parameter
Pn001.0.
DB resistor disconnected
Check if excessive moment of iner-
tia, motor overspeed, or DB fre-
quently activated occurred.
Replace the dynamic brake unit or
change the external dynamic brake
circuit. And reduce the load.
DB drive circuit fault
−
A defective component is in the
dynamic brake circuit inside SER-
VOPACK. Replace the SERVO-
PACK.
Wiring of the dynamic brake unit is
incorrect.
Check the wiring.
Correct the wiring.
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.
The I/O signal cable length must be
no more than 3 m.
(cont’d)
Problem
Probable Cause
Investigative Actions
Corrective Actions