11-25
11-4 Troubleshooting
OMNUC G5-SERIES AC SERVOMOTOR AND SERVO DRIVE USER'S MANUAL
  11
Troubleshooting and Maintenance
The Servomotor 
holding brake is 
ineffective.
Power is supplied to the holding 
brake.
Check whether power is supplied to the 
holding brake.
Configure a circuit that cuts power 
supply to the holding brake when the 
motor stops and the load is held by 
the holding brake.
The motor does not 
stop or is hard to stop 
even if the operation 
command (RUN) is 
turned OFF while the 
motor is rotating.
The load inertia is too large. Check the following:
·Is the load too large?
·
Is the motor rotation speed too high?
Review the load conditions, and 
replace the Servomotor and Servo 
Drive with appropriate models.
The stop circuit failed. − Replace the Servo Drive.
The motor is 
producing unusual 
noises or the 
machine is vibrating.
(Continued on next 
page)
There are problems with the 
machine's installation.
Check to see if the Servomotor's 
mounting screws are loose.
Retighten the mounting screws.
Check whether the axes are misaligned in 
the coupling.
Align the coupling.
Check whether the coupling is unbalanced.
Adjust the coupling's balance.
There is a problem with the 
bearings.
Check for noise or vibration around the 
bearings.
Contact your OMRON dealer or 
sales office.
The gain is wrong. − Perform manual tuning.
The Speed Feedback Filter Time 
Constant (Pn103) is wrong.
Check the value set in Pn103. Return the set to 0 (default set) or 
increase the set value.
Noise is entering into the control 
I/O signal cable because the cable 
does not meet specifications.
Check to see if the cable is a twisted-pair 
cable or shielded twisted-pair cable with 
core wires that are at least 0.08 mm dia.
Use a control I/O signal cable that 
meets specifications.
Noise is entering into the control I/O 
signal cable because the cable is 
longer than the specified length.
Check the length of the control I/O signal 
cable.
Shorten the control I/O signal 
cable to 3 m or less.
Noise is entering into the cable 
because the encoder cable does 
not meet specifications.
Check to see if it is a shielded twisted-pair 
cable with core wires that are at least 0.12 
mm dia.
Use an encoder cable that meets 
specifications.
Noise is entering into the encoder 
cable because the cable is longer 
than the specified length.
Check the length of the encoder cable. Shorten the encoder cable to less 
than 50 m.
Noise is entering into the signal 
lines because the encoder cable is 
stuck or the sheath is damaged.
Check the encoder cable for damage. Correct the encoder cable's 
pathway.
Excessive noise on encoder 
cable.
Check to see if the encoder cable is 
bound together with or too close to high-
current lines.
Install the encoder cable where it 
won't be subjected to surges.
The FG's potential is fluctuating 
due to devices near the 
Servomotor, such as welding 
machines.
Check for ground problems (loss of 
ground or incomplete ground) at 
equipment such as welding machines 
near the Servomotor.
Ground the equipment properly 
and prevent current from flowing 
to the encoder FG.
Errors are being caused by 
excessive vibration or shock on 
the encoder.
There are problems with mechanical 
vibration or Servomotor installation (such 
as the precision of the mounting surface, 
attachment, or axial offset).
Reduce the mechanical vibration 
or correct the Servomotor's 
installation.
The motor is 
producing unusual 
noises or the 
machine is vibrating.
(Continued from 
previous page)
The machine and the motor are 
resonating.
Check to see if the machine is resonating.
· Readjust the torque command 
filter time constant.
· If there is resonance, set the 
Notch Filter 1 Frequency 
(Pn201), Notch Filter 1 Width 
(Pn202), and Notch Filter 1 
Depth (Pn203).
Symptom Probable cause Items to check Measures