Mitsubishi Electric FR-E700EX Instruction Manual page 84

Speed control
(4) Troubleshooting
Condition
Motor does not run at the correct
speed.
1
(Command speed and actual speed
differ.)
The speed does not accelerate to
2
the command speed.
3 Motor speed fluctuates.
Hunting (vibration or acoustic
4 noise) occurs in the motor or the
machine.
Acceleration/deceleration time is
5
different from the setting.
6 Machine movement is unstable.
Rotation ripple occurs during the
7
low-speed operation.
82
Possible cause
(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) Torque shortage
The torque limit is activated.
(2) Only P (proportion) control is
performed.
(1) Speed command varies.
(2) Torque shortage
(3) Speed control gain is not
suitable for the machine.
(Resonance occurs.)
(1) Speed control gain is too
high.
(2) Motor wiring is incorrect.
(3) Mechanical resonance
occurs.
(1) Torque shortage
(2) Load inertia is too high.
(1) Speed control gain is not
suitable for the machine.
(2) Response is slow because of
the drive unit's acceleration/
deceleration time setting.
Speed control gain is too low.
Countermeasure
(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.
(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.
(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)
(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).
(1) Raise the torque lilmit level. (Refer to page 111)
(2) Set acceleration/deceleration time suitable for the load.
(1) Adjust Pr.820 and Pr.821 (Refer to page 80)
(2) Set the optimum acceleration/deceleration time.
Raise Pr.820.