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Speed control
(4) Troubleshooting
Condition Possible cause Countermeasure
1
Motor does not run at the correct
speed.
(Command speed and actual speed
differ.)
(1) Speed command from the
controller is different from
the actual speed.
The speed command is
affected by noise.
(2) The command speed and the
speed recognized by the
drive unit are different.
(1) Check that the speed command sent from the controller
is correct.
(Take EMC measures.)
(2) Adjust bias and gain (Pr.125, Pr.126, C2 to C4) of the
speed command again.
2
The speed does not accelerate to
the command speed.
(1) Torque shortage
The torque limit is activated.
(2) Only P (proportion) control is
performed.
(1) -1 Raise the torque lilmit level. (Refer to page 111)
(1) -2 Capacity shortage
(2) Speed deviation occurs under P (proportional) control
when the load is heavy. Select PI control.
3 Motor speed fluctuates.
(1) Speed command varies.
(2) Torque shortage
(3) Speed control gain is not
suitable for the machine.
(Resonance occurs.)
(1) -1 Check that the speed command sent from the
controller is correct. (Take EMC measures.)
(2) Raise the torque lilmit level. (Refer to page 111)
(3) Adjust Pr.820 and Pr.821 (Refer to page 80)
4
Hunting (vibration or acoustic
noise) occurs in the motor or the
machine.
(1) Speed control gain is too
high.
(2) Motor wiring is incorrect.
(3) Mechanical resonance
occurs.
(1) Set Pr.820 lower and Pr.821 higher.
(2) Check the wiring.
(3) Set and adjust the notch filter (Pr.862, Pr.863, and Pr.871).
5
Acceleration/deceleration time is
different from the setting.
(1) Torque shortage
(2) Load inertia is too high.
(1) Raise the torque lilmit level. (Refer to page 111)
(2) Set acceleration/deceleration time suitable for the load.
6 Machine movement is unstable.
(1) Speed control gain is not
suitable for the machine.
(2) Response is slow because of
the drive unit's acceleration/
deceleration time setting.
(1) Adjust Pr.820 and Pr.821 (Refer to page 80)
(2) Set the optimum acceleration/deceleration time.
7
Rotation ripple occurs during the
low-speed operation.
Speed control gain is too low. Raise Pr.820.